The mod for
this MP game (currently turn 9) is ~650k and contains 8 mod nations which introduce 374 units, 20 magic sites, 146 weapons, 50 armors, 123 spells, and 510 sprites in addition to making 12048 lines worth of changes via CBM. All of the above numbers have hard limits, but hard limit for the total size of a mod seems very large. I have not experienced it.