How do I properly lay a tongue and groove plywood subfloor remodel when joist layout is not always 16" oc?
A sketch would help us better answer your question, but per manufacturer installation instructions T&amp;G subflooring should be installed so that the T&amp;G are perpendicular to the joists. 

The tongue and groove support systems are not meant to support weight between joists for more than 24", and by the sound of it you are hoping to have a T&amp;G joint that is the whole length of your room. Do not do this!

You should never have two panels butt together between two joists where the joints run parallel to the joists. Those panels should both be cut so that they each lie on half of the joist. So you get 1.5" of the first panel on the joist and 1.5" of the second panel on the same joist.

Simply put, cut your subfloor panels so they both rest on the odd spaced joist. If your measurements above are accurate, you have about a 12'x &lt;8' room. You will need two pieces of 8'x4' subfloor to complete the job.