The backlash they would receive from the community would be monumental, the nerve they have to do such a thing, rather than fix their problem they are profiting from it, makes me rethink that this is a solvency issue and not a banking issue
Somewhere in the thousands of pages of commentary about Mt. Gox's recent issues someone made an argument that a bulk of the fee did not go into Mt. Gox's coffers. Rather it was largely the charge demanded by a financial institution who was able and willing to perform the fiat transaction. Said institution is used sparingly by Mt. Gox...for obvious reasons.
I have no idea if there is any truth to this and don't remember who proposed it. Probably user 'sturle' as he is among the most vocal (and informed) of the Mt. Gox advocates. In fact he is about the only one here on this forum it seems.
It is also recent scuttlebutt that even with the 5% fee transactions are no longer going through. At least for some people. I don't find difficulty imagining that Mt. Gox has relationships with large, important, or historic customers which are not as negatively impacted as their relationships with the small fry.