My thoughts (Link main in Melee, picking up TL in Brawl for stupid ICs...):
Utilt - less ending lag - string it better then. Would also makes it great for utilt->dair (if faster jumps).
Jumps - slightly higher base jump, higher second jump (as far as he can tell he doesn't jump much better than Ike, yet Ike's recovery is way better when they're both low). Jumps faster.
Up+B - Frame one would be nuts (so good OoS), but maybe Frame 6 is still good? (that'd be Pika dsmash speed...). Make it go both higher and farther. Charging would be interesting, but don't then make it like Diddy's recovery (needs to charge to not suck). Actually just don't use charging as a reason to make the uncharged version suck. Semi-spike on it?
Hookshot - maybe bring back the ability to grapple stages? A few frames less lag on ground, but don't add lag frames to landing after aerial hookshot.
Side+B: No more gale boomerang - I'd prefer a more 64/Melee boomerang - and throw it faster - but if it is gale boomerang maybe 40% chance of tripping (not a random trip because it's forced) if you try to jump while being touched by it on the way back? (Combo set ups, risk of jumping out, etc.). Also would drag you in shield (think it already does so) to set up grabs.
B: Arrows are fine, but buff them - faster etc... Trying to think of something cool for this... Maybe building off of PixelPasta's idea, Link charges himself up with Neutral B and while fully charged, press B (charge is whatever, maybe giant punch time or something, one to six frames (ie could be 1,2,etc. for the activation) and you start to fire sword beams? Could then deactivate it by pressing B again (maybe like 12 frames, but three frame to deactivate and nine lag) if you think you might get hit to keep the full charge instead of having to charge again (also if you want to go in for a smash or something where trades may occur). Charge would dissipate upon being hit while it's active, but not until then. So unlikely but would be so cool.
Down+B - let Link bomb-jump (or buff his recovery even more than I could hope). Bombs should knock people either up or toward the bomb - knocking them away promotes camping more than it should, but up/toward is more comboish.
Other stuff - Fair come out faster, dsmash kill earlier (maybe they used Pikmin Order (just kidding mantlecore77)), Fsmash first hit has more IASA frames, nair should be Melee like, would list more but don't want to completely spoil Link, a lot of what has been previously said seems pretty interesting
Spoling Link, but give Link a jab-grab? As a whole, he needs first and foremost better up+b recovery range, and then other stuff - getting gimped so early just sucks...
