Here is a theoretical rpg moveset for Mario and Luigi

The Man in Red
Stat Strengths
He has very balanced stats, no major weakness to speak of
Stat Weaknesses
He dosnt much in the way of major streghts outside of stat boosting items
Special Moves
Fire Ball
A special move, mario throws a ball of fire at the enemy of choice, it causes a chance of burning
Fire Ball Blitz
A action command where rapidly pressing the action button floods the enemy with fireballs, causing massive damage
Super Jump Punch
A specual punch that has a higher chance of critical if the enemy is flying
Fludd
A rapid stream of water is shot, it may be weaker but it can make the target skip its turn
Super Cape
Creates a cape that can protect himself, if a enemy target himself with a projectile it gets deflected
Cape Shield
Have the cape barrier an ally
Cappy
If given a special hat he has the unique property of possessing and copying the powers of an enemy (think of Poo's mirror)
Final Smash: Fire Wave
A all target hitting fire attack, can cause burning on all targets

The Man in Green
Stat Strengths
Faster than Mario and has more Hp as well
Stat Weaknesses
Slightly less attack stregth than mario and would rely on special moves slightly more
Green Thunder
This thunderball differs in that its hits multible targets with tiny chance of paralysis in exchange for less accuracy
Luigi Rocket
A chargeable move that can cause stunning to the target, it however has a bit of recoil damage
Luigi Super Backflip
An action command, by tapping the button in rythmn you can real high with a super backflip before choosing a target to crash land on, can cause confusion
Green Tornado
A Exploit that causes very tiny damage to all enemies but only confuses the target
Luigi Punch
A special move that has low accuracy but instead if it connects always criticals
Taunt
A Explout where luig rapidly goes though a bunch of poses and either confuses the target or lowers himself a chance to be hit
Final Smash Negative Zone
Instead of the Poltergeist, Luigi uses his special powers of being in his brothers shadow to create a zone where all enemies get confused
This is a very rough version of what special moves these two characters can do, I decided to both reference their smash and normal movesets so please give any feedback if you want