There is certainly the idea in RP that blood matters more than clan, and that doesn't have to be that way. It could stand to discourage people, but personally, I like the idea of someone adopting a culture and a loyalty and integrating in to a clan.
Critical mass of RPers is a really big thing too, the Minmatar RPers we have are divided certainly. Like, if you have 5 people in GRD, 5 in RE-AW, and 10 in UNITY, an 10 in various single person corps, it will have much less effect than having 30 active people in one corp/alliance. This critical mass was something that certainly once existed in UNITY, and -EM- and to a lessor extend even groups like Terra Matarr managed to generate a sort of RP gravity around them with the sheer personality and presence of their members.
This is something, that can be achieved, but there will probably have to be some commitment from people who want the faction to grow. To this point, I can't really say much, my main is in a Caldari FW corp, not particularly against the Republic, but she isn't really pushing the Minmatar as a faction, merely a culture. There is also the point that not everyone is willing to deal with the realities of being involved in PVP, mining, RP, or Industry. One corp makes it difficult to do it all. An alliance probably can, but even if you look at the Amarrian RP groups arguably the strongest community ATM, CVA does null, PIE does FW, SFRIM does highsec, and so on.
I read about older stuff like the The People's Republic of Minmatar and it makes me think the potential is certainly there.