Doubtful, SM. His more likely programatic approach would be to create a new namespace (the actual location in memory where the user variables are stored) for each user variable referenced, then when the blend is done he simply "lets go" of the old one.
As it stands, there's probably only one namespace for user variables (so they're shared during blends, and hang around even when a preset hasn't been shown for 5 minutes) and that namespace has a limit of 23 entries.
If Ryan doesn't respond to this quickly, it would only take me a few minutes to cobble together a script that goes through presets changing all of the user variables to names like User_1 User_2, etc or something like that (perhaps we could agree on a list of common ones like angval, timer, etc and leave those alone) but that would create the new problem of a value the preset can't handle being in that variable when it starts, and also probably cause issues with blending. (Of course, one might argue that such presets should be corrected anyway.)
I strongly suspected that the user variable namespace was somehow a problem, as I've ran into the situation when editing mega-presets where I often change names that past a certain point new names would simply stop working, but I had so many things on my mind I didn't think to mention it here. Sorry