My game wont allow me to upgrade my Thieves Guild Armors more than once... and I want to make them the best they could naturally be, but two of my armor pieces that fortify enchanting have low/below 25% smithing enchantments... so is it cheating to use a fortify restoration potion that makes my low% pieces equal 25% before I upgrade.... your thoughts?

I actually already did it... but felt kind bad afterward and stopped playing.... I may just re-load before the up grade.

IMO, it makes no sense to talk about cheating in a single player game. If something spoils your enjoyment of the game for whatever reason, though, don't do it.

I wouldnt do it because its a bug.
I dont think it is intended to work that way.

But its a single player game and you should do what you want in your own game.

Just be careful with these kind of things, the popular bugs in Oblivion like duplication or infinite money could corrupt your savegame, because the game is not designed to work like that.

I'd feel like cheating, which would svck the fun out of the game for me, so I wouldn't do it.

It doesn't really matter what you call it though, it's a single player game, do whatever is most fun for you to do.