7000 photos model production

Hi, I'm working on a terrain model. I have 7000 photos taken with the Phantom 4 pro. I have a working area of 5000m x 500m and 25 ground control points.

I think I'll do it faster if I make all the photos aero piece by piece. I'm thinking of merging the resulting blocks.

Do I have problems in merging between blocks?

I need to add gcp for each block and then merge it later, or should I add gcp after merging and do aero again. ?

thank you.