Here are my answers to your questions:
- I'm not sure. That came from Joshua, who is the only one who has really created the files.
- I'm not sure why removing this would make writing significantly easier. If a file were loaded, there would have to be an flag on that file line to let the app know it was shared geometry.
- Yes. However, this is related to item 1, which I didn't have a good answer for. I can't remember how LDView would behave in this instance. Note that LDView strips out the 0 !: from the beginning of all lines they occur on when it is in a !TEXMAP region before parsing those lines (although it also keeps an original copy of the line text).
- This command would actually be quite useful to allow an editor to add a sticker to a user's model. One !TEXMAP PLANAR NEXT, and one quad. It could also be used in an official part with a blank fallback, but only if we allow blank fallbacks (which is probably a bad idea now, but may not be in three years).
- Every method would have a different number of parameters, but any renderer supporting such a method would know in advance how many parameters to expect. Any renderer that doesn't support such a method should either simply ignore the !TEXMAP command, or present a warning to the user. Right now LDView semi-parses the CYLINDRICAL command, but that is an accident; I forgot to remove that code, but will do so prior to the official LDView 4.2 release, which will result in an "unknown texmap method" warning from such lines.
- I agree.