You'd be surprised. The graphics pipeline has changed; GL1 was designed around the FFP. DirectX changes so much as to be impossible to salvage old code, from version to version. OpenGL has remained "compatible", but a lot of what you do is emulated software-side. For example, pr_linelist, pr_linestrip, pr_trianglelist, and pr_trianglestrip are all that's left, hardware side. And the strips are on their way out. It's getting to where your only choice is between lines and triangles.
Anyway, reading over his request again, I think you're right. I don't have any intention of supporting that, presently, as it removes the possibility of link-time optimization. Specifically, inlining graphics calls. Compared to the actual work done processor side, this is small, but it still aggravates me. It also bloats the game from having two of the same thing in it, although the amount of duplication has been improving, lately. In the event I get around to actually making a game in ENIGMA, my inclination will be instead to release two versions. This is assuming that neither (1) I determine that the game doesn't need mind-blowing graphics, and GL1 is fine, or (2) I determine that if your shit doesn't support GL3, it has no business attempting to run my game.