To improve Yoshi, my idea is this...
Midair Jumps
Instead of one big second jump, why not make Yoshi's jump truer to his game persona? I propose he get multiple midair jumps that mimic his flutter jump from Yoshi's Island. He would hover forward a good distance and then gain significant height (though not as much as he does now) toward the end. Maybe give him 2 or 3 of these jumps.
This helps his recovery and allows for interesting aerial approaches on the ground after a SH since I'm thinking there shouldn't be any DJC. Also helps in edgeguarding.
Egg toss recovery would work the same and using them before midair jumping would still work to preserve jumps. This gives Yoshi pretty good and flexible recovery.
Shield
I would say let Yoshi jump out of his shield, but also remove the entire shield-shrinking mechanic for everyone and essentially give everyone the same type of shield Yoshi currently has. Blue shield turns more red as it take damage. Bright red means the shield is about to break. I think that's fair.
Moveset
Standard - Jab Kicks into Side Kick
Same as before except we add a third attack similar to his old f-tilt from Melee. High priority.
F-tilt - Tail Whip
Quicker with more range and less lag, perfect for setting up air combos. Damage and knockback are both very low. High priority.
D-tilt - Tail Swipe
Same as now, a quick get-off-me move. Improve the knockback to make it a KO move at higher percentages (200% or more).
U-tilt - Tail Flip
Make this look more like a violent f-tilt angled WAY upward. Quick with more knockback than previous but slightly more lag. Does high hitstun and juggles at low percentages. Kills at 150%.
Dash - Rushing Heabutt
Same as before
F-smash - Yoshi Kick
Yoshi leans back on his tail and lets loose a kick with both his feet. Startup is quicker than you might think and knockback is good. Kills at 110% and doesn't lag much. Attack comes out instantly after a full charge (much like MK's f-smash in Brawl). High priority.
D-smash - Double Tail Sweep
Increase the knockback a bit (somewhere between Melee and Brawl) to make it a reilable KO move. Kills at 120%. Very quick coming out but leaves you open from above if whiffed. Very little lag, though.
U-smash - Head Smash
Same old move it's always been. Kills at 115%. Comes out fast, huge hitbox but lags a bit.
N-air - Yoshi Boot
Same as it ever was, kills at 140%. High priority. Useful after a double jump as an approach. No lag on landing.
F-air - Head Dunk
Same as Brawl. Non-sweetspot kills at 120%, sweetspot spikes and kills off the top at 175%. Can be autocanceled.
B-air - Tail Frenzy
A series of quick tail whips that deals mediocre damage and knockback but has high priority and does great hitstun. Sets up combos and kill moves. Autocancels. All-purpose move for Yoshi.
D-air - Flutter Kick
A multi-hitting move that has high priority and deals massive damage if all hits connect. Hitstun is low so it's easily punished if you land next to someone. Lags on landing.
U-air - Tail Somersault
Quick vertical kill move with great vertical range but narrow horizontal range. Autocancels and kills at 115% off the top. Great juggler at low percentages.
Specials
B - Egg Lay
Unblockable command grab. Quick with about the same range as the standing grab. Egg pops out right behind Yoshi and just above the ground, allowing a small window for opponent DI. Can hit the egg but damage is reduced by about 50%.
SideB - Egg Roll
Changing this entirely. Yoshi rolls forward a moderate distance in an egg and automatically pops out with a bit of lag. Quick startup, high priority, decent vertical knockback and high hitstun. Egg automatically turns around at an edge. Moves forward quite a bit if done in the air. Useful for recovery in the air and approaches on the ground.
UpB - Egg Toss
Same as Melee except that it helps recovery like in Brawl. High hitstun, making for great edgeguard setups.
DownB - Yoshi Bomb
Same as Brawl. Kills at 115% when it hits when done off the ground, 150% it if hits after it's done in the air.
Grabs
Standing Grab
Still slow but a bit faster than before with less lag. Has a long active hitbox.
Dash Grab
Yoshi takes a step, leans forward then grabs. Great range, a bit of startup and lag if it misses.
Pivot Grab
Still amazing. Comes out quickly with almost no lag.
Throws
F-throw
Decent knockback and high hitstun. KOs at about 170%
B-throw
Same as f-throw except in the opposite direction.
U-throw
Decent vertical knockback with decent hitstun, allows for combos at low percentages.
D-throw
Low diagonal knockback with high hitstun, useful for setting up u-air kills.
Alt. Colors
Green
Red
Yellow
Blue
Indigo (or dark blue for you philistines
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)
Purple
Pink
Orange
Black
White
That's all I got.