Great questions. I've got a 12 valve i want to drop in my Excursion & am hoping someone has the same answers. From what i've read, the 24 valve can actually run with less than a dozen wires connected. But i have no idea about grid heaters, cruise control, or running an Allison for either the 12 valve or 24 valve with either PCM.
I'm starting to lean toward keeping the 4R100. $4,000 for a BTS, $425 for a stand alone computer, $500 for a fordcummins.com adapter. Hopefully that would be it. It is possible that a chip can be burned so you keep your Ford PCM & run your 4R100. PATS will probably have to be disabled by the chip.
Baumann's kit has you cut the 4R100 harness & splce them all to their controller. You can tune it with their software. This definitely gives you the most control. You will still have to beef your transmission for the Cummins. My 4R100 is behind a 7. 3 & was seeing temps over 200 even with a Factory Tech Accumulator Valve Body with a little over 110k on it. Now with a BTS torque converter my temps are staying below 170 for the most part with over 220k. I still need a rebuild.
One of the main reasons i want the 12 valve is to get rid of the electronics controlling the engine. If i did a 24 valve i'd want to convert it to a P7100. Like you however, i have no idea how to get some of the regular controls to work. I'll be checking back to see what you discover. -Matt