The 5050 was -is-remains exactly that......a rumor. Certainly so much so (no mention by Epson of anything...) that you don't want to base your immediate future plans around it.
The 5040 is a real deal....and inexpensive enough to warrant...even justify an 4k upgrade down the road.
And....if you haven't used the spare Lamp by then, it will be an even more irresistible quick seller on the AVS Classified.
As for remounting the DEA, you'll be best served to scale down the size just enough to effect a full wrap around your Frame to achieve a Border-less, zero edged look.
The image area of the 117"er is 58" x 102". While that's not huge, with the DEA you want a very flat, "squared face" and the issue with building a 3/4" Flat
frame is two fold.
- You have to get the Corners square and the Kreg Screws in straight. Any twist at all is magnified down the Length...and the height, and when helped along with the medium tension you want to stretch the DEA with, again, any thing "off" will show.
- You have to use a Quarter Round Trim for a Standoff.
Simply put, a fully Flat frame presents potential issues. You have to design one right, and assemble it right just to get the best results, and with a DEA, done right and set-up right, it's among the very best of it's type.
Now this is what I suggest. It happens to be close to your own idea.
Hand picked straight Poplar lumber in the 1x3 size can be the largest side used. The DEA likes a firm, even stretch, so 1x2s on edge for the exterior, and 1x3s laid flat to the Rear Edge for the interior vertical supports will work nicely. You'd want 4 Vertical "Interior" Supports. You'll build 4 Corner / Front edge assemblies.
So....here's a drawing to help things along.