First of all, I am very excited by this news. I believe there is an opening for a WWI flight sim, and if it came from HTC, who has crafted what is the best all-around WWII flight sim, so much the better.
Like it or not, I believe HTC has more customers to gain by expanding into WWI than it does by adding the Heinkel, or the Oscar, or the Brewster. The latter will serve to satisfy customers who are already here, the latter will attract new ones.
I believe it has to be done right to be worthwhile though. The immersion is a must factor for anyone attracted to this arena. First and foremost, to make it challenging and hold the interest, the planes need to have all their quirks and flaws modeled in. Flying a Camel doesn't need to be like flying a 100mph Spit, etc and so forth. The terrain graphics update underway will help, and since AHII planes are already so graphically detailed and the new cockpits are so nice, I think we can check this box. I believe any WWI arena should be an axis vs. allied setup, for the reasons already mentioned. A historical map with the nice new terrain, aerodromes, ballons, and of course, No man's land. I believe that because almost week by week innovations was such a part of WWI, RPS should also be used.