Is the format that hard coded that you cannot change it to something like: HaasVF199.f86?
Which portion is limited to 99 numbers, the uncxXX or the fXX? If either of them allow a rename or both allow 99, then you have 99^2 combinations.
How many machine tools are identical and can use the same post-processor? We used to have 2 or 3 of each machine model and each machine model used the same post, so for 8 machines, we may have had 3 or 4 posts.