Just realizing...
I have a 'rule of thumb' bit of code that gives you a valid TIG (and PEG-7 target) for a de-orbit based on optimizing over parametrized trajectories (in the implementation, you can ask MCC for a de-orbit solution and it'll tell you what to use). This has an accuracy of perhaps 100 miles (well within the cross range), so this leads to something an AP should be able to handle.
I don't know how strong your coding skills are to read source code in an exotic language or how confusing the references to external functions are, but... it's just about 100 lines, and it should be moderately easily adaptable by anyone interested.
https://sourceforge.net/p/fgspaceshuttledev/code/ci/development/tree/Nasal/mcc.nas
(specifically the function mcc_request_process_deorbit )
I guess the interesting bits are the desired periapsis determination and the relatively simple TIG determination (compute REI assuming you'd de-orbit now, get TIG by minimizing that error).
I really appreciate your help. Unfortunately my coding skills are ZERO.
Maybe this could be useful to the SSU team though..