I would want to see something else than just the Alien books for that price. (especially, as this option only appears now when both Alien Reprints are on the market)
Perhaps, Marc can dig into the GDW library and add some extras that would make it all worthwhile and differenciate from what is already on the market. For instance, adding a worldbook section on Luna, Kusu and including some of TNE stuff on the Inkur. Having a reprint of the articles on Vland and the First Imperium, he wrote up could also be nice, if he could include as a bonus add-on.
And, I actually bought the Traveller's Aid Encyclopedia, which was the German hardback with all the Alien Modules plus Alien Realms plus the Alien Handbook for 200 Dm. Granted that was stiff, at the time, I understood that it was from a smallish publisher, just like T20 and my money would be supporting Traveller.
Lastly, with all the delays that a hardback may entail, I would question whether it could really be a seller. So, I echo the above concerns and say that the Traveller Adventure & Traveller Book. Or a corrected MT, in hardcover would be a better venture.