Well, answering to myself: No it's not possible.
The only VPN stuff that contains portal with browser features I mentioned (actually an java or activeX plugin that handle your NIC and installed a TUN driver) are Juniper and Cisco.
2links to explain what i wanted:
http://cisr.univ-lyon1.fr/guichet/doc/pinsa.pdf
http://www.cict.fr/IMG/pdf/VpnDidactNC.pdf
(once time, it's in French 😉)
Thanks!