So I got this idea from this video... But I kind of really wanted to apply it to Transformers. Garry Chalk: BW Optimus Primal + Cybertron Soundwave = Primal Sound Richard Newman: BW Rhinox + Cybertron Vector Prime = Vectox Scott McNeil: BW Dinobot + Cybertron Snarl = Dinobot Snarl Ian James Corlett: TM Cheetor + RID2015 Shadow Raker = Shadow Cheetor David Sobolov: BW Depth Charge + Prime Shockwave = Shock Charge Susan Blu: G1 Arcee + BW Transmutate = Tarncmutatee David Kaye: BW Megatron + Animated Lugnut = All Hail MYSELF! Don Brown: BW Scorponok + Armada Cyclonus = Cyclonok Doug Parker: BW Terrorsaur + Armada Tidal Wave = Terror Wave Jim Byrnes: Beast Wars Inferno + Beast Machines Thrust = What if Inferno survived the Beast Wars instead of Waspinator. Colin Murdoch: BW Quickstrike + Energon Scorponok = Quickstrike now with 50% more scorpion. Brian Drummond: Beast Machines Jetstorm + Cybertron Jetfire = Animated Safeguard?
I think the more interesting thing to do would be to think of what their personalities would be. So using one of your examples, Primal Sound would be one of the sole survivors of Planet X, committed to protecting peace and ending war to ensure that the fate that befell his planet never befalls any others. Still talks like a DJ but his personality is more like Optimus Primal, but maybe willing to use some of Soundwave's more questionable abilities like mimicking voices and stuff.
I kind of did that with David Kaye... more as a joke... but I do imagine that given Lugnut's blind loyalty to Megatron that being combined with a Megatron would make him self obsessed instead. I think he would still have Lugnut's intelligence but Megatron's affinity for rubber ducks and saying "yes" in a weird way. So would Primal Sound be a Maximal like Optimus Primal, a Decepticon like Soundwave, or someone more neutral who could probably work for either faction for different reasons?