It would be nice if administrators could temporarily disable the account creation limit for particular IP addresses.
This would be particularly useful in situations such as that described in bug 16569. Ideally, we would be able to apply an anonymous-only block to the affected IP addresses, leave account creation enabled, and ask people to create accounts in order to contribute. However, the account creation limit was hit by each of the IP addresses within hours of the problem first arising. We thus have to fall back on the tedious process of asking people to e-mail a mailing list to ask for an account to be created for them.
If an administrator could indicate "yes, this IP address is producing lots of account creation attempts, but please allow them all through for the next 24 hours", or something along those lines, it might alleviate the problem.
Another situation in which this might be useful is when a school wants each of its students to create an account for a class project of some sort. I recall several occasions where this has been done; in at least one case the limit was tripped and an administrator had to offer to manually create the remaining accounts for them; I don't recall if they were taken up on their offer. Being able to temporarily turn off the limit would be a cleaner solution.
Just a thought for next time.