Well tbh, Every player in the eWorld should move to poland to take advantage of the bonuses.
That Poland would then span the globe leading to a whig-nightmare of complete peace under pax-poland would be awesome in itself.
However players stay in their nation because of 'because' and whils the economic costs of moving are (as the Baron points out) not economical compared to an alternative - You have to weigh it against the retention cost involved of making something fun, kewl and unique happen.
Better 15K spent on deploying some troops then having them get bored, disintrested and die. Do that and you end up with.........well what we got now to be frank.