You have some great ideas for the ceiling... Be careful using the 6 x 12 room... it has common denominators!!
You should change the dimensions of the future control room to eliminate coincidental resonances in the space. Treatment can not fix those issues. It helps, but does not 'fix'.
I would recommend that you research the level of sound proofing that you require. See my resources page and download "How To Find How Much Isolation You Need", along with anything else that you would like. 🙂
CR / TR sight lines and symmetry:
Sight lines are very important during production... but a CCTV camera and video monitor can often be better than a window. It is very important to maintain symmetry in the control room, but NOT in the tracking room. Form follows function.
I would not recommend iso-boxes for guitar re-amping. Use a real room! You'll have low frequency issues if you do and the recorded speaker never sounds like it does in the open room. You'll probably need a good isolated booth and I would recommend that you contact me or any other reputable studio designer for some plans. 😉 - It's a lot cheaper than trying and failing. 😛