The consesus seems to be that the functionality of the bubble shield is better than Yoshi's egg. But it would be better to have shields that actually make sense to the characters.
Obviously we can have both. Theres no reason why Yoshi's shield functionality can't be made the same as the bubble.
Hey that sounds pretty cool! I got a few:
1. Peach hides in Perry from Super Princess Peach
2. Game and Watch's Donkey Kong 3 will encase himself in a bubble. (Then again, this is based on the modern one. ^^')
3. Zelda's Naryu's Love, a non-attack version.
4. Lucario's replacement will use protect. (Possibly Zoroark)
That's all I can think of.
Great ideas. Don't understand the Game and Watch thing, but you could take virtually any object from his games and use it as his shield.
Just quickly off the top of my head:
5) Sonic - Pulls out one of the infamous sonic Rings to protect himself. It's about time they made an appearance in his moveset.
6) Mario - Pulls out a red koopa shell. (He can wear one as armour in Super mario RPG).
7) Link/Toon Link - Obviously uses his shield. It's bizarre he would use a bubble shield over his own one isn't it?
8) Ike/Marth - Just crouch and hold their swords accross themseles. When an enemy hits them the swords snaps at light speed into position to protect from it.
9) Squirtle and Bowser - Hide in shells.
10) Ivysaur - Giant protective leaf that he wraps himself in.
With a bit of imagination you can come up with something for almost all of the characters really.