No worries, happy to help
Seems to me it should work (and rickeb1 may be on the money, definitely worth checking). How best to set it up depends on what you want with what on any given patch. With MP1 in the GSPs loop, the MP1 is getting its input and output GSPed. Are there effects you use in the GSP while using the MP1 as a per patch alternate, and what does the GSP do to the sound before it goes into the MP1 ? Also if you want TC effects on both the GSP and MP1 you could put the TC after the GSP before the power amp (and use a real time continuous control midi pedal to control the TCs master volume).
A slightly more complicated solution which gives allot of flexibility (of what and how much of what you want) is to use a small mixer (bit of a hassle with a stage rig but I've used a small 8 channel mixer for years, velcroed to the bottom of my rack). For your set up, a mixer with 6 line inputs (or 4 with a stereo effects return) and 2 aux (effects) sends. Then split the guitar input signal so both the GSP and the MP1 get their input straight from the guitar (I'd proffer the MP1 will sound better this way), GSP ch1/2 MP1 ch 3/4 TC in from aux 1/2 TC out to ch 5/6 or eff retrn L/R. You can then adjust what level you want for each and send both the MP1 and GSP to TC. If you want to have just the MP1 or GSP make a midi patch that picks a "blank (no volume)" program in the one you don't want to hear.
I use a (old now) Yamaha AM802 mixer, works great for this kind of rig. 8 mic/line ins, 3 pre fader aux (effects) sends, 2 stereo effects returns. I find it's so much easier to set it up this way and get your gain structure right, but does take a little space...
On the compressor/EQ front, compressors have their place, I'm not a big fan of using them on guitar as the flatten the dynamics and take away tops (ss and tts in vocals) and the ones that take away less are very expensive, also, if you drive a valve hard so it's distorting/clipping (which is what we ADAers do
) it's already compressing big time. The high gain circuits in the ADA have a midrange eq boost as part of the voice (good description in the manual), some ADAers like to use an EQ as well, very much up to your taste. Personally I've alway had plenty of EQ in the MP1 and now MP2 (and while the MP2 also has a 7 band graphic built in as well as the standard tone controls), I don't use it much. RanallRG (Steve) likes his MXR 6 band ? There are a few posts from other dudes who like EQ, some discussion on a nice old peavy EQ for example...
Pickup choice has a big impact on note articulation (as does how you play). E.g. EMGs (active) are favored by some very high gain players as they give good articulation and also work well with dropped tunings. However, if you try the MP1 as your primary (i.e. plug straight into it) > TC (wet dry mix in TC) > poweramp, crank it up, you may find that part of the articulation problem at high gain is with the GSPs distortion circuit ?