I wish you a lot of success!
A question you will definitely have to answer (you had better write the
answer on the website): Is the BIOS free software? I believe the answer is
"no" given Intel's attitude towards coreboot... and I understand that Intel's
graphics is what is best supported by Linux-libre, hence the choice.
Is the choice of an older CPU really justified by Secure Boot? I mean: as
long as it lets you install a free operating system (and one even comes
installed by default), what is the problem?
Technologies in Intel vPro such as TXT (
https://en.wikipedia.org/wiki/Trusted_Execution_Technology ) and AMT (
https://en.wikipedia.org/wiki/Intel_Active_Management_Technology ) are to be
avoided but you can still find i7 processors without them.