1000x1800! wow! Mine is going to be 1000 x 700 because that all the room I have. I’m going to re-make the y-axis end plates as well, but I’m using 1/4" tool-plate alu, using the designs someone else posted (probably you!) to the forums. I’m also doing the plate between the X-axis makerslide that you talked about here I had a piece of 6mm tool plate machined down to 0.163" so that should fit well.
Clever idea with the drill mount! What I wish I had was a universal spindle mounting plate that mounts on the Z-azis, then additional plates that you use to mount whatever tool you want. This plate would be pin registered with the main universal mounting plate, and locked down with four socket head cap screws. Something I may have to work on when I get my X-Carve upgrade someday…