Well, I already have such kernel for N770 http://fanoush.wz.cz/maemo/#pptp
and there is no problem to make it for N800 too. Just nobody asked so far. I did it few minutes ago, check the url above.

Kernel contains enabled crypto API, extended brightness patch and mmcplus stuff from http://intr.overt.org/blog/?p=54

For pptp you need to insert extra modules as described on the page. It shouldn't be a problem to do it in some script before you call pptp client. You'll probably make some script with pptp client call anyway.

As for the bounty - I didn't do it for the money so even if it solves your problem there is no need to pay anything. If you want to send something then see the bottom of http://fanoush.wz.cz/maemo/