I would imagine that most of the users who come from America (and probably more from outside our shores) are familiar with the concept of Rollover Minutes when it pertains to mobile phone plans. The idea is that if you do not use all of you minutes in a month, they will get "rolled over" to the next billing month, allowing you to use those rollover minutes in case you go over your limit in the future.
I think that we can take this concept and apply it towards the idea of rep limits here on StackOverflow. The idea is that if you hit your rep limit, but then continue to gather upvotes for that time period, those extra upvotes could be "banked". These banked points would then be used to offset downvotes that you cast and downvotes cast against you (and other reputation droppers such as a deleted post costing you 100 rep).
Daily Rep Limit = 200
You have accumulated 200 rep through 25 up votes (50 rep not counted due to limit)
If you receive a downvote, your rep is now down to 198 and it will take another future upvote to push it back +2 (wasting another 8 points) to get you back to the rep limit.
Note: If you have 215 rep via 25 up votes and an acccepted answer, this turns out even worse because you'll be dropped to 213 rep without any chance of boosting back up that +2 because you are still technically over the rep limit.
Daily Rep Limit = 200
You have accumulated 200 rep through 25 up votes (50 rep "banked")
If you receive a downvote, your rep remains at 200 (Banked rep now = 48)
If you have 215 rep through 25 up votes and an accepted answer, I would also hope that it could correctly calculate your "new rep limit" of 215 so that you could be prevented from losing that 2 rep (which would knock you down to 213) and have no way of making it up.
Also, any further upvotes (again now that you have hit rep) would be applied to your banked points.
Banked rep can only be used during the same day it was banked (this would prevent someone from accumulating hundreds of banked rep points which could prevent them from ever really losing any rep again)
If necessary we could impose a bank limit, which would only allow you to have X points banked at any one time (say 50 or 100).