Yeah, steel is required for late game buildings, units, etc. But the same could be said about wood. Civilization doesn't have a wood resource for a reason: forests(which are made of wood, usually) provide production. Same goes for iron and stuff. There are some things(such as swordsman) who require resources in order to represent a
certain rule the resource had in history. Also, the whole conversion idea would simply make some resources more valuable from others.
Plus, wonders don't increase crime but amphitheaters do?
Some suggestions:
1. Make crimes increase with progress the player\ city made in the respective subject: vandalism should increase with SPs, corruption should increase when your treasury gets too big, theft should increase with each building produced, etc... This would serve your goal of preventing snowballing much more than making buildings simply unworthy of building(come now, 3 crime points from a building yielding 1 culture?! You should notice how crime shapes the game, because from my experience thus far it makes some strategies almost useless...)
2. Wonders should increase crime. I get the feeling that the great wall is visited much more often than a public school, and it also attracts much more attention.
3. Certain events reducing crime? I'd imagine that some, such as WLtKDs and GEs should do so...
4. Shouldn't high loyalty decrease crime? Look at the soviet union, for example.

5. You said crime replaces maintenance, but it applies to(nearly) all buildings, including those which didn't have it before. With sovereignty (or otherwise), will there be a certain way of reducing the crime that such buildings(markets, banks, etc.) Provide while also reducing the profits they provide?
6. Shouldn't conquering cities cause certain crimes(mainly treason, abduction, violence, and... The rest

) to increase? You might point out loyalty's rule, but there's much overlap in this area(or at least, there supposed to be much overlap).