You could add a +3 strength ability to the hero while hes carrying the item, and remove it when he drops it, however there is no way of directly adding the ability to the item.
just go to object editor, click the items tab, find gloves of haste, and at the top of its editor thingy is item abilities, find item strength bonus +3.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.