So many things to respond to! I think I'll just field tidbits here and there rather than commence some funky manifesto...
NH has been invaded by MA--and others, but to that end, there is still a kinship. A large percentage of MA natives that I have met that now reside in NH have actually altered their own perceptions and value systems--The NH mystique if you will, has these generally more liberal folks acting the part of the yankee conservative--even to the extent of claiming native status and deferring in general to many of the existing trends--a 'when in Rome' mentailty. In NH, MA folks are resented to a degree, but nowhere near as much as NY, NJ, and points South residents--same goes for VT and ME...we have a kinship amongst ourselves, but it is more inclusionary on a regional basis and more exclusionary on a wider basis.
Folks here don't ask where you're from and then sneer if they don't approve of the answer...it's pretty obvious who's who based on anything from your license plate # to your last name (my last name is 6 letters and 2 syllables and has never been properly pronounced outside of New England).
Anyways--I caution you on assuming that a state as rich in history and culture as NH would open its arms wide and accept any size group let alone 5~20 thousand. I know for a fact that there are few locations that could absorb that size a population increase--the move alone would likely cause backlash with the local incumbent officers to create growth moratoriums, and there is no one area outside of Berlin that could handle such an influx. There is a housing shortage in this state--a severe one. My town is currently enacting a moratorium on new developments in an effort to stall the enormous impact upon infrastructure that this wanton growth creates.
Lastly for the moment--to attempt to quantify NH or any New England state by looking at census stats is to grossly misunderstand how we think and function around here. For instance--I'm a highly educated professional NH native, registered repub right now, was ind. before the primaries, will vote down fernald, support shaheen, jeb bradley, voted for mccain and then gore...when I was a VT resident for a few years, I helped elect Bernie Sanders, Pete Clavelle and Howard Dean. And I'm not alone...as the last Pres. primary revealed, as well as the election of Angus King in Maine, the tremendous support for Jim Jeffords in VT, and a staunch refusal to enact income and sales taxes in NH in spite of the would be risk to the educational funding system.
In short, if you all come to NH, VT or ME, you will likely find yourselves assimilated to us long before any of us embrace your philosophies.