I can help where I can.
If I had the h6315 phone and want to improve things this is what I would do.
Do exactly the types of things you described.
Look at the thread I referenced above. I listed the tool I used to tweak the CAB file. You can download trial.
A couple things might be happening here:
1) Try removing the registry script, it might not be compatible with your phone. You can also view it and learn a bit.
2) Check out this thread too this is a slightly older Stack but I think someone made some progress on a h6315 (most interesting info here is about the registry, there may be another over there too about what's in registrtry for the BT stack)
http://forum.xda-developers.com/viewtopic.php?t=14329
3) Check the verizon stack (a zip)
http://pdaphonehome.com/forums/attac...&postid=275444 It's possible these patches (from i-mate) are not complete and are relying on components already on the HTC phones. The verizon patch might incude a possible missing file.
4) Try trimming the fat off the kit even further. This is guess work by the names.
Lots of hard reset between experiments.
I also thought I read somewhere of a new patch for the hp phone out. I forget where, something about "3700". Maybe build 3700. Might have been at xda-developers.com