I was under the impression that ME7 with wideband support (eg. the RS6) uses sensor values instead of modeled values when applicable already.
I could be wrong, and BAM, s3 etc might be different.
RS6 doesn't do that, EGT is only used in ATR.
Thought about patching it into BTS, but never got to it. Model is quite accurate anyway.
EDIT: bleh, went to reply before reading till the end. :\
Oh well, then here's the idea to implement "real" EGT into BTS:
Quick and dirty hack that comes to my mind: find reference to FBSTABGM and replace the axis lookup "mov r14, tabgbts_w" with "mov r14, tabg_w" (or tats_w).
There are couple downsides to this approach, but it generally should work (that is, if you have wideband EGT sensor already functioning with stock code).