There aren't even enough SR IV mods in existence to require a mod manager...
Nothing wrong with using something ahead of time to be prepared for such things.
I find it hard to believe something doesn't already exist honestly, if the game is highly moddable and there are mods available, why not create a mod launcher with more control, seems like a no-brainer.
Gentlemen of Fake Steelport
Or you could ask the user for which sections of the xtbl file to use and build a new one from that. For example you could read the <name></name> tags in weapons.xtbl and ask which ones to use.We could make something that attempts to merge xtbl files and updates asm files. If the merging process were to fail, you'd have to do it manually anyway.