It is only for the sake of different TR versions that we need a common equiv file

Anyone generating texture packs has a version of TR. They have to capture textures as part of the process, and can generate their own equiv file, using the texture deleting trick on textures they want to handle differently.

So what we need is one common equiv file that has all the ties between TR versions, without those between the levels. Then an author can combine the version equiv file with their own pack-specific one, to creat one that will give the same behaviour as their own, but indepedent of TR version. (The join facility of the tool does the correct type of combining).

There is a fairly easy way to generate the inter-version-only equiv file.

What you do is capture Level 1 for all versions of TR, and generate an equiv file from that. Then do the same for Level2. Then Level3, and so on.

When you have them all, you just concatenate them all together (deleting the header on the first line from all but the first.

That's close, but doesn't quite completely solve the problem. In some cases a single texture occurs more than once in a single level, and authors may want to map them differently. I think you have to, to solve the M problem in the Colosseum.

To deal with this, we would have to treat such a level specially when generating the inter-version equiv for that level. Probably the easiest way is to edit one occurence of the texture (from each TR version).

That's rather awkward, but the nice thing is, the resulting altered version-equiv file would still be useable by all authors. Wether the separated occurences of textures would remain separated would depend on the pack-specific equiv file it was combined with.