There is no specific reason that expansion shave been a PO2 doubling, other than standard programming logic to think in powers of two. What is your application for combo aliases, that you have expended them all?
If increased, I would try to set this sort of thing up as a standard value, along with the other combo placement modes. Quite frankly, I would think that users more easily run out of tiles, than anything else. I know that I, and a few others have certainly done that, because we use an unsigned short for them. Given the data width of a tile, I see the sense in limiting them for quest packaging, but because we compress that data, and unused space should be 0, I also see the 'nonsense' in it.
Combo aliases are the same sort of deal. I'd rather hear the rationale both for, and against a change here.
I'm not against this change, despite that I rarely use the things, mostly because I'm senile and forget to use them. We may as well get all out filepack revisions done in one pass; but it will not be in a maintenance release (e.g. 2.50.3), as this would pose compatibility concerns within a series of releases that should be avoided.
I'd like to add some extra padding into the filepack to support changes within a series, in the future. I would be in favour of increasing all the system counts, if they do not gravely, adversely affect file size.