This is an interesting point and, to be honest, I think it kind of hurts Reimu's chances. Say Reimu is added, people think she looks really cool, but there's no real way to actually support the series (in the west) outside of a few fan games. If some of the original games got an eShop release proper like the Neo Geo arcade classics, I think Reimu would be in business.I agree with a lot of your post, but this part is probably a bit more relevant to what I'm about to say.
It also doesn't help that a huge amount of the western player base resorts to piracy (For fairly obvious reasons). It's not exactly a series you can tell someone to get on steam (Though, that has changed, but still only in Japanese). Telling someone to pirate a game to be able to play it isn't something a lot of people would be willing to do, even if it is as simple as downloading an executable. It's really only within the past 3 years (When NISA released Genso Rondo) That Touhou has been officially penetrating the western market rather than through the essential Internet Black Market.