Cool, got it. 
IMHO, this is extremely hard to set right. Let’s say the deposit fee is $5 indeed, and let’s take a popular trading platform as an example. Users are frequently depositing funds, so the $5 is probably too much to ask (centralized services offer lower fees). On the other hand, if the platform is popular, $5 could be totally acceptable for a malicious competitor - she needs to invest only ~$29k to completely halt the transfers on the platform for the whole day ($5 every 15 seconds). It might help if these fees can be chain-specific (operators and/or users can define what suites their use case best).
Yep, I guess this needs to be thought through. Seems to me like some messy situations could happen, but I might be wrong, of course. And what about the concurrency problem (everyone tries be an operator)?
Oh, I see. Now that you you’ve explained this to me, I wonder:
- Why the exits are processed exactly at min(blocknr + 40320, current block + 1)? What if the current block = blocknr + 4 (this will be the min and the exit will be processed 60 seconds after it was submitted)?
- Why we need to be sure that blocknr + 40320 is not accepted?
Please keep working on this, it’s really exciting and important!