That's a great idea! Never even crossed my mind. I've read about the vacuum sealing but they all said it was expensive so I just dismissed it. You thought outside the box for sure and came up with a good one!
Since my cut pieces often provide part of the pattern for the next piece, I do gluing as I go. I squeeze a minimal amount of glue on a piece of waxed paper and use a toothpick to run some glue around my window (the hole in the background veneer). I only put glue where the new piece touches either the background veneer or an already placed piece. I insert the piece and then, as mentioned earlier, I rub a little extra glue into the joints from the back side. If needed, I stick a piece of blue tape over that for a few minutes until it sets. By the time I am done, everything is glued to another piece, the background veneer or both. Then I sand the back so I have a smooth surface ready to glue to the substrate piece (plywood, mdf, whatever).
Before I do that (glue the project piece), I glue another piece of veneer to the back of the substrate, put a piece of waxed paper over the veneer and add cauls. Then I clamp the heck out of it. After about an hour or so, I unclamp and trim the excess veneer. Then I put glue on the other side of the substrate and attach the project piece and repeat with the waxed paper, cauls and clamps. After that I trim the excess and glue strips to the sides. I just "clamp" that with blue tapestretched tight. I do two opposite edges first then trim them. Then I do the other edges and trim them. I am still working on the best way to trim the excess from the sides. I've had some problems with that.
I'd like to hear more about how the vacuum press works and how you use it if you don't mind explaining.