Now that we have PC Notes, I consider this request obsolete. However, I can elaborate a bit on why this limit actually exists.
All internal MIDI messages are 4 bytes long, of which the first 3 bytes determine which internal "device" ("devices" in this context are cutoff control, reso control, filter mode control, dry/wet ratio and plugin parameter automation) is used. So theoretically there are 128 automatable parameters left (the high bit of the last byte is unused). However, there are two variants of the first two bytes, of which one indicates that the macro is an "extended" macro. This extended macro is used for accessing parameters 128 through 383. Now theoretically one could add more extended macros, but I'm not sure what kind of consequences this would bring and if it's necessary at all.
