There should be a way for kirby to absorb almost everything in the game in have it be good. For example, having him absorb characters would give them just thier B move(but in return, make them more useful for him. Faster/stronger/etc). But, absorbing projectiles or items mode give him power-ups from his kirby games. Example: absorbing the Beam sword would give him his swordsman costume, which would change all of his attacks. Absorbing IC's blocks would give him Ice Kirby. Ness's PK Thunder? Spark Kirby!! PK Fire? Fire Kirby! The results would make for some very compelling gameplay because you could radically change Kirby just like that, making your opponent change their playstyle. Sup, mindgames?
The same could be said for Yoshi, kinda, however, instead of gaining abilities, if he ate the item, he would lay an egg behind him. That egg would get modified properties of that attack. It would be similiar to Yoshis Island in that eating an enemy laid and egg behind him, which he could throw. When, he doesn't have any eggs behind him, his egg throw is just the normal Eggs. When he has eggs trailing him though, he'll throw the "equipped" egg. Yoshi can have a max of 5 Eggs and if he's standing next to the ledge with his back turned, the eggs will hang off(edgeguard opp). The eggs can be attacked and destroyed but when attacked, they explode into sparkles like normal eggs. Yoshi would also have a roll eggs attack, which would roll the egg slightly, stop and explode. Doing this in the air would cause the eggs to drop vertically, exploding when they hit someone or after a period of time. This would replace his rolling egg attack.
Projectiles and Items that would "Equip" to Yoshi
Mario's Fireballs- Fire Egg This is why I said "modified proterties". Eating Marios fireballs would be useless if they replicated them exactly. As a result, these eggs would serve somewhat as a Pan-spike or Judgement#6 from Gaw, sending them horizontally and a slightly downward angle, dealing 8% with med knockback.
Doc's Pills- Launcher egg. This egg would be kinda like Yoshis normal egg except in launches the NME up slightly, setting up for juggles, dealling 8%.
Baby Shadowball- Dark egg. When this egg explodes, it would send about 6 baby shadow balls all around it. They wouldn't deal much knockback but they would each hit for about 6%.
Med shadowball- Shadow Egg. It would hit with the force of a medium shadowball.
Full Shadowball- Death Egg. Full Shadowball %age and knockback.
The same thing applies to Samus Charge shots and super scope.
PK Fire- Maletov Egg. This would explode into about 4 PK Fire pillars.
PK Thunder/Thunderjolt- Thunder egg. would have the same properties of GaW's Judgement#5(The thunder mallet. Not 9)? It will always go a certain distance before exploding(about 2/3 FD). The egg has almost constant hitstun so it could potentially drag them and then explode, dealing 2% per hit and the explosion dealing 12% and knocking them up..
Chef- Eating GaW's sausage would heal Yoshi for 10% per sausage.
Oil Panic- Panic Egg. This would take on the properties of the Oil Panic attack.
Soft Missile- Homing egg. The egg would home in and deal 12% w/ medium knockback.
Hard missile- Hard-broiled egg. Takes on the properties of Samus's hard missile.
Bob-omb- OMG Egg. The egg takes properties of the bob-omb
Star-rod star- Star egg. Egg explodes into 6 star-rod stars. Each star dealing 5% with med knockback.
Star Rod- Stiff Egg. Takes properties of throwing a star-rod, dealing heavy horizontal knockback.
Fan- Take properties of throwing a fan, dealing high Vertical knockback.
**** this. I'd add more but then I realized that, this ISN'T GONNA HAPPEN.
You guys get the idea though.
I think about this stuff too much...