Have you paid any attention to what Vivec said? He specifically said the intented limit would be 300, not 50. Which is nearly two and a half times NPO's current member count.
Let's be honest here, no small alliance would merge past the 300 member mark for a variety of reasons including but not limited to just not possesing that many members, (which i would like to mention has never happened before.)
Moreover, the whole point of this suggestion is to limit stuff like NPO's 1200 man alliance, not prevent micros/smaller alliances from merging.
I'd suggest you re-read his suggestion with a clear mind.