It's a nice initiative!
First of all, Strategy First is just the US publisher, it's G2 Games which owns the rights to EE2, so it's them we have to contact.
Then I see some problems. Publishers are often reluctant to reveal numbers sold, so we'll probably have a hard time getting any numbers from G2 (or Strategy First).
Then I'm not so sure EECH is such a huge hit at GOG. Will probably have a hard time getting actual sales numbers also from GOG, but the number of user ratings should give some indication. Currently EECH has 194 (
http://www.gog.com/en/gamecard/comanche_vs_hokum) and 154 for EEAH, compared to some of the more popular games which have thousands (e.g.
http://www.gog.com/en/gamecard/fallout). Compared to some other simulators it's not too far behind though, IL-2 has 574, and Red Baron 338.
Or another way, which doesn't tell numbers, but gives relative sales performance is to select browse games, and sort by "bestselling" (
http://www.gog.com/en/catalogue#all_genres/order/bestselling/). EECH is a little below the middle of the list.
Also there is the point that GOG sells EECH for $6, while G2/Strategy First sells EE2 for significantly more, so even if EECH sold more, it might be argued it's because it's much cheaper.
I think what we have to convince them is that EE2 isn't selling any more (hopefully true

), and is practically dead. They can resurrect it and generate more sales (for no cost!) if they release the source code. And we also need to convince them that there is no more comercial life in the EE2 engine, so they are not tempted to release another version of a sim based on it themselves. Because if they want to create more sims themselves they obviously want to keep the source code, so that a modded EE2 doesn't compete with their latest release.
Arneh and other's great work is easily transferable to EECH2.
Easily transferable isn't quite it, it will almost certainly be a significant amount of work to move all the work over. But possibly less work than writing a new 3D engine for EECH, which is sort of what we would get (the only thing we really want from the EE2 source code is the more modern 3D engine).