This is getting a bit off topic. My original point was that mechanically you are able to equip enough UMD gear to allow you to bypass the class/race/alingment restrictions of certain item and then equip said item. Once that item is equipped however, players are able to remove that gear and lower their skill below the skill threshold held that was originally required. By utilizing base ranks instead, however, the character in question will always have that level of UMD and better represents how a character would both equip and continue to use that item.
Equipping certain gear for certain a situation is only logical and makes sense. My suggestion was based around the fact the players can long reap the befits and rewards of the UMD skill after it has been lowered, when they should in my opinion not be able to. If for example you were wearing a "Ring of Seeing Eyes", you do not continue to have the dark vision feat associated with it after its removed. You used the piece of equipment for its purpose lose its benefits. UMD class/race/allignment emulation DCs are different in that they are a different kind of check. With spot/influence etc., frequently you make one check to see if you pass or fail and that's it. They do not continuously check to see if you still are able to see that sneak you already noticed without any change in the situation.
In my opinion, wearing a locked piece of gear should require you to have a the requisite skill at all times. Constant skill checks are an extreme drain on the server however. So by using base umd ranks instead current score, the character will always have the required use skill at all times. No further checks required.