It would be impossible to balance something that's really Meta-Game, that is your extensions effect your in game performance, but nothing you do in game (a minor fee for unlocking the extension aside) can effect your EP gain and allocation. Allowing an in game process, such as a NIC sink, to effect EP would be impossible to balance. The act of reallocating EP would become mandatory for min/maxing. If you limit how often a reset can be done, all that's done is fix the planning period. That is if you can do NIC based reset every 90 days, then you would plan your character around your current EP + the next 90 days, then plan again. What this ends up doing is completely removing the 'wait' for level 10 extensions, making your character maximally effcient with each reset, then adding back in the lower levels as the EP is earned. If you don't reset, then your 'behind' because your sitting on 40,000 EP waiting for level 10, which your opponent already has, but with only 3-4k unspent EP.
EP adjustment should be to correct for small changes in balance from patches, not for whole sale remodeling and 'trying' out different builds on demand.