Now that you said it, it's true.
Bowser Jr should be Bowser's son, yet he's using a vehicle that resemble Eggman's.
If Eggman using his usual vehicle, it will feel to similar to Bowser Jr.
EGG-HVC-001 with a quick-switch ability would be more interesting.
I like to believe that Sakurai regards Smash Bros. games as an "ecosystem" and that his choice of characters and movesets for each character is to not upset that ecosystem by having characters too powerful or weak, make other characters too powerful or weak, how the pick-up items work etc. That said probably the reason why Bowser Jr. is in the clown car and not fighting like his dad is probably because with the clown car he has a moveset that best fits him in the Smash Bros. ecosystem. Not only that but it allows the Koopalings to be echo fighters on behalf of Bowser Jr.
Dr. Eggman for Smash Bros.That said I'm not saying that Dr. Eggman's default vehicle should be the Egg-mobile while fighting and move around like Bowser Jr., my suggestion is the
EGG-HVC-001 be his default combat mech. The EGG-HVC-001 could be modified to be more agile and throw standard punches and kicks. Think of it like the
E-Mech but it's likely most are more familiar with the HVC than the E-Mech. The HVC can also come in a variety of colours such as default red, Good Future purple... those are the only ones I can think of.
I also suggest that Dr. Eggman will have a "quick switch" ability to be able to switch to various mechs from past games to best fit a moveset that can fit in the Smash Bros. ecosystem.
For example, I can imagine the
Eggmobile-D be used as a side-special where Eggman drives along the stage terrain, has a launchable drill and once 18HP of damage is sustain will break apart and revert back to the HVC.
While the HVC could probably perform regular jumps, Eggman could perhaps have limited flight which would temporarily disable the HVC for default Eggmobile. And while up above can perhaps use
Fire dropper and/or the
Spike dropper for aerial moves, where Eggman can drop hazards down to the stage. Fireballs will create a small area of fire damage or the spike balls be regarded as hazardous objects, perhaps with physics.
As for standard aerial attacks, I don't really know. Maybe the use of
Hammer,
Big Arm or
Egg Hornet for standard aerial combat.
As for Final Smash...
Wrecking ball! The ball will automatically swing but the player can move Eggman left and right to apply more momentum to the pendulum.
Just saying Dr. Eggman would have a more versitile moveset for Smash Bros. if he brings his tech along.
Metal Sonic for Smash Bros.This is more easy. Simply an echo fighter for Sonic the Hedgehog. Super Sonic can simply be replaced with the
V. Maximum Overdrive Attack but still functions the same way. Metal Sonic may have different run animations due to him mostly using his jet than legs to move about but introducing Metal Sonic along with Dr. Eggman would keep in theme with him.