Galactus said he was upgrading Surfer and prior to that Surfer did upgrade himself with the blackbody he absorbed in prepping for his fight with UniLord. he also absorbed all of UniLord's souls but I think he released them, not sure.
anyway, yes... if the Motherbox is that good then it might give Tony the edge, but it sounds just like a GL ring... I want to know more about its limitations (of which there are some, I'm sure).
IM's tech is great but he's not got the sort of all humbling win-loss record with it, when confronting major powers, to put him in the prep-threat category of someone like Doom. Doom's tech-prep almost always results in a victory for Doom. IM's usually results in a few chuckles for the reader (Hulkbuster, Thor-buster, the armour he fought Storm in... not that Storm belongs in the same class of threat).