[TYPO3-dev] End user page access, but with my own DB and Session variables?

[rubengoethals at pandora.be]

Hello all,
 
I am developing a central login for my web pages.  Unfortunately, I couldn't
use any extensions because I have like 13 different typo-3 independent end
user DBs and I do need all these DBs.  Merging them in 1 DB is no an option
since these (mysql) DBs are also used in various other software and accessed
via several places with several use cases (not only for the website!).
Also, this would lower performance.  Anyway, I managed to write a login php
for it (1 DB with references to all other DBs).  Only I have a problem with
allowing typo3 (admin) users setting access according to my login system.
 
My question more precisely is:  If I have a certain session variable set
after a successful login in my own login page, is there any (easy) way I can
use that to make it possible and easy for typo 3 (admin) users to set or
unset access to a certain page that would for him transparently use my
session variables?  
For example, can I make something so that typo 3 presents my possible
"session variables", being like user groups (each of my DB is a different
group), as items  in the "Access" configuration (under "Visibility
settings") of a page, under 'items' (there were one can find fore example
"Hide at login", "__Usergroups:__", etc; see screenshot) ?
If not, any other ways ?
 
I don't mind fiddling with typo3 php pages, but I guess that's clear.
 
Thank you very very much for any help.
Greetings,
R U Bn