TPM2 + Secure Boot via systemd-cryptenroll is the closest to the “just works” FileVault/Android experience. Keep a recovery passphrase in your password manager. You don’t lose your data if the motherboard dies, you just use the recovery key.
I use this on my daily drive laptop. Only real hiccup is that I still keep the dual boot because fwupd does not cover my laptop BIOS firmware updates but in a Linux tablet this a no issue.
Just use the OCuP4V2 dock, it has the proper mount to secure the GPU and the PSU. No enclosure, your cat either need to leave it alone or you will need to be creative.
If you are into eGPU, and is firm about the 13/14 size don’t get the Framework. This “Pro” version is disappointing, not coming with USB 4.2 or TB5, Dell released last year a Dell Pro 14 with 2 TB5, they will probably release more this year and Lenovo will announce their Thinkpad 2026 lineup tomorrow: https://mactivity.lenovo.com.cn/smb/thinkxp-c.html?pmf_group=in-push&pmf_medium=sc&pmf_source=Z00028090T004
What are you about here? “Just a simple metal plate”, what exactly are you expecting? That is exactly the definition of a motherboard or a dock.
The TGX dock from Lenovo is that inside a box.
I never said TB5 is best than Oculink in performance but is better than a TB4 and reduce the gap to Oculink. Good luck with your imaginary eGPU dock and your Framework 13 with limited TB4 port.