I guess times are mature for me to pass to Diablo I wanna have Tear and the latest Quickclip, and other goodies that aren't available for Chinook.

Since I don't want to lose even half a day with my tablet blocked in the process of upgrading (geez, I use it for true!), I thought I could prepare a nice full install of Diablo on my previous tablet, a n800, obviously on a sd card to have all the space I need, and, when everything is ready, copy this filesystem to the sdhc card of my workhorse (n810).

Is this idea too naive? Are there problems or incompatibilities I am going to encounter? Should I abstain from such a procedure?

Any hint is welcome, and thanked in anticipation

I've flashed an N800 with an N810 diablo image and it worked fine, except I had help for N810 (which is probably minor considering). But as you are doing this from SD, you will need to flash the flash to diablo as you'll need the diablo initfs and kernel.