Look
if u have Ultimate Unwrap, the x exporter will perfectly convert the x to b3d.
There's an Ultimate Unwrap special version posted in the very last thread about x exporter, very recently, some days ago, at elysiun forums. Go there, to python and plugins section, dig for that thread, probably yet in the first page of that section, as was some days ago....
BTW, I happen to find better for my purposes a modification of the x exporter made by this guy...it has even settings and a gui fo rthose problems u mention.,...and others.
here:
www.mindfloaters.de
I use that one (1.2.1 x mod exporter) often.
That is: Having Ultimate Unwrap, and some trial and error (like usual with x format and most packages, specially with bone-weight-anim stuff) , it works quite well for producing B3Ds... (or just x, cal3d, md2, ms3d, md3, md5 if u also work for othe rengines)
It's allways bout finding the right plugin, and doing some trial and error.
Oh, I don't think u'll have a problem programing plugins for python: you actually would benefit a lot, as u can increase blender functionality in the way u need, and not wait till some one else is in the mood for it...sharing then with comunity, is a nice detail ;)
edit--- argh...mindfloaters site is down...well...a zip I made now with all the plugins I like for games...many are not online anyomre, so better grab this....the good x exporters are sepcially direcxexportermod, or something like that....also u can try with the UU3d version...though I prefer the other.
There's also other obj and 3ds plugins that I prefer to native, also md2 and md3, both with anim (the md2 even with md2 anim import, md3 I think only exports md3.All these exporters work very well. Not included md5, but u can find that one easily digging for der_ton posts at Elysiun. )
Grab this:
(left click, don't right click, not here, nor in the next page at download hosted file link)
http://uploads.savefile.com/redir/127076.zip