delegate count also affects confirmation time. The more delegates the longer you must wait for confirmation and the longer you must wait for random numbers.
You can still use 101 delegates (the half for the confirmation...) on every block confirmation...
Let's say because of added delegates you have right now 404 "active" delegates...
you split them in 4 equal blocks (see graph)... 101.101.101.101
and you pick one random* block (of 101 delegates) to make what you do right now (the "dirty" work)
In the long run all delegates will be paid the same average amount because all had the same opportunity...
The only thing that changes of course is a little bit
higher standard deviation on payments amounts
*PS the confirmation time should not change significantly