Okay, after being on the road for 4 days and using this daily, I'm happy to report it works well.
I can't give you the files because it's all really just renamed files from .threads with some changes and documenting the changes would take a little bit of work and I'm swamped right now (besides, I'm using a heavily modified older version of the code and not the latest build).
But, basically, what I did was take each file that would be used to read/post message, read/reply/send PMs and copied the original .php (15 scripts) and .tmpl files (15 tmpl files) with a mob prefix. Then I edited the templates and php files to remove the img references, rework the templates to not use more than one column and fixed any links to only those used by the mobile interface. I also cleaned up the php scripts to make them a little more efficent to reduce load times. Overall, I only had to make a small change to the send_header function in .threads and the rest is just modified scripts that have been renamed. Cell phones do use cookies, so I didn't have to do anything special for that.
The result is that people go to the wap page and stay within the grouping of "mob" scripts and templates. The changes to the php scripts are minimial - I removed the footer calls and modified the send_header function in ubbt.inc.php to look for a superglobal for "ismobile" when determining which header to send (regular headers or just the compact version). The tmpl files are all pointing to the mob* scripts and the php script are all pointing to the mob tmpl files.
I'm not saying it was easy, it took me about 5 hours of solid work; but hopefully this gives you an idea of what I did.
