Think you only learn "common-sense" from the mistake(s) you make/witness - assuming you survive them
Just for what it's worth, I would go with not suitable for environment for having (I assume metal) CU in an bathroom in which temperature and humidity vary sharply over a short period of time, just look at level of condensation that appears on bathroom mirror, cold taps, etc, when shower or hot taps are turn on - even with a decent extractor fan.
Of course this can all be mitigated, if the everything is allowed to climatise as per manufactures specs (if manufacturer actually provided you with specs for this - good luck), but I'm not aware of any domestic environment that takes this into consideration. Could argue with CU in cupboard the it's 'protected' from sudden change in bathroom environment until you open the cupboard door - who would open the door to the CU just after a hot steamy shower? common-sense lesson in the making.....
Cut a long(ish) story short, not something I would be willing to do.