Well I could certainly see Hatton giving Cotto some problems early on in the fight, but again Cotto would only let Hatton do his deed and IMO Cotto would get in on the fight from like the 5th round and on and beat Hatton.
Hatton would know that his best chance is to get Cotto early which means maul, ruff up, forearm, pushing off with the elbows all of that to get Cotto early on.

Pernell, I will assume that when you say top Welters you mean top 10 (Unless you worded that wrong)

I'm not sure how you have the Welters rated but I think theres 3 top 10 Welters Hatton would definitely have a good shot at.
Gomez
Isaac
Zab

I could def. see Hatton beaten these 3 guys.