Not too keen on the Matrix, but here's probably how I'd do it: Certain Transformers display signs of Matrix Affinity, meaning that they are potential bearers of the Matrix of Leadership. Only Transformers who display signs of Matrix Affinity can truly become Primes and access the wisdom of the Matrix, but how exactly those signs manifest is a mystery. Some believe it to be by divine birthright, while others believe it to be something that comes about through heart and deed. Regardless, it is known that only Transformers with Matrix Affinity can become Primes. During the war, most Transformers with Matrix Affinity were Autobots, but there were a few Decepticons (Thunderwing) who displayed them as well. Once an Autobot (because the Matrix belongs to the Autobots) is identified as displaying the signs of Affinity, they are rebuilt with a Matrix chamber. Transformers are not built with Matrix chambers, they need it to be built into them later on. They may also receive a physical power upgrade during this surgery due to the fact that they may become Supreme Commander. The Matrix itself, however, does not provide its bearer with a physical upgrade; it only grants them access to the wisdom of the past Primes.

Same answer as in the Prime/Convoy rank thread: the ancient Primes were grandmasters of the Matrix Templars crusading against the Quintessons and their Forgespawn heirs, while Great War-era Primes were super-soldiers whose upgrades were based on Optimus's own self-inflicted upgrades (and Optimus himself continued working out the bugs until he reached what he felt was the point of diminishing returns).

During the age of the Dynasty of Primes, the position of Prime was hereditary. Primes would specially construct their heirs and encode them with the Primal Essence, an operating system used exclusively by members of the Dynasty. Under the Autobots, the position of Prime was an elected office. Citizens of the Commonwealth would elect a council known as the Primal Conclave. The Conclave would meet in the Primal Basilica and sequestered until they chose the next Prime. Any Commonwealth citizen could be selected by the Conclave, the only requirement was that the Prime-to-be had to consent to become Prime. Once a Prime is chosen, they are immediately sworn in and serve for life. When a Prime dies, the First Senator of the Senate becomes acting Head of State and elections of the Primal Conclave are held. During the Maximal Era, the right to appoint the Prime would be given to the Imperial Senate, who would then always choose the current Magnaboss of the Maximals for the position.

I really only think Hot Rod should be the one upgraded by the Matrix himself. He's the chosen one, his rise should be special, not the standard. It also helps emphasize his struggle if he's forced to "grow up" too fast. Everyone else it should either have no physical effect or they need to be upgraded by external forces either before or after receiving it.

You're only saying that because you aren't ready for such ambitious ideas like... uh, Bumblemus Prime, Arceeus Prime (Two e's Nintendo, please don't hurt me), Ironhideus Prime, Jazzus Prime or even... Wheeljackus Prime.

The matrix is a living force, sone believe it’s connected to Primus but no one cane be certain It is believed that very few (one in a Millennia” type of thing) autobots has an affinity or some type of compatibility for the matrix but this is just a myth perpetrated on the masses by the Autobot elders and clergy to protect the matrix from falling into “unworthy” hands The truth of the matter that the matrix is a living force, a live looking for a symbiotic relationship with those it inhabits abd that nearly 50 to 75% of the transformers are physically compatible of not only useing the power of the matrix.....it being used by the matrix themselves The matrix is equally capable of being influenced by and or influencing its host so it was decided to create a “myth” around the matrix to hide its true nature, but the matrix has fallen into decepticon hands in its histiry Leading to catastrophic events

I think I am going to go with the mythical route here. The only real way for a Cybertronian to become a Prime is if they fill out certain qualifications that the Matrix deems worthy of the title. Like for starters, bots don't always need to have traits like honor, compassion, and virtue but the Matrix will certainly not choose individuals who revel in slaughter and destruction. Due to the blessings from Primus, the Matrix has the ability to subtly bestow the title of Prime to a medium pool of individuals, this would mostly go unnoticed by the larger general population except said individuals that are given said title, along with some powers that comes with it.

I agree with SPLIT LIP's suggestion of the Matrix upgrading its wielder being a Hot Rod-exclusive thing, since he's literally the Chosen One, the one meant to Light the Darkest Hour. For every other Prime, they either have to be rebuilt to withstand its power (Optimus Prime, I'd assume Elita-1 too) or win the Forging lottery and be given a body capable of handling it (Ultra Magnus, Thunderclash from IDW). It's a receptacle forged to contain the wisdom of a line of rulers stretching back eons. Your average schmuck off the street doesn't have a body capable of processing that much information.

Following the first 13 leaders of Seibertron, the 13 who freed Seibertron from the Quintessons, the Primal Vanguard was formed in their honor. A military meritocracy and hierarchy, it selected those at the top of the chain considered most worthy to become the Prime, giving them the Matrix, the core of the computer Vector Sigma, containing the sentient AI within the computer, called Primus. It contained all of the Cybertronian race's collective knowledge, and thus only Primes are worthy to wield it.

Optimus can be the role model, Rodimus can be the friend, but all Primes are meant to lead their people through the darkest hour. It's how they do it that defines them; let's say for example Sentinel was a authoritarian dictator, but was fair and kept his people together.

How "Things We Don't Tell The Humans" handled it: The Prime is the religious leader of Cybertron, connected and selected by Primus and all the Prime's that came before, serving with a Protectorate who helps rule; the Protectorate ensures the Prime does not become lost in the dogma and forget the common not while the Prime makes sure the Protectorate remembers that there is more to life that the one. A Prime doesn't need to be refitted or altered but sometimes the Matrix will do so if it feels they need a new form to lead. Till All Are One is the creed of the Cybertron Religion now as it speaks of when things will be put right again. The reason Ultra Magnus couldn't open the matrix us he is a Protectorate type, not a Prime type

Oh boy... I never even considered this idea. XD Hmmm... as for how I would handle the Prime process... I would say that the Prime could be of one of two groups: those who are groomed by the High Council to be the next leader, and those who are chosen by chance. Those who are picked by the Matrix itself are considered the true wielders of the Matrix's power. The Matrix can upgrade a Prime to a new body if it so chooses, but most of the time, it does not. Most new Primes have to have new bodies built so that they can handle the power increase that comes with it.

I liked the idea of the Matrix Templars from the Universe comics where Cybertronians with an affinity for the Matrix are given training. In Regeneration, Optimus Prime kind of did this with Hot Rod.