I think I didn't make myself clear enough about what I had in mind.
What I meant was some kind of an "emulated" TAP32 driver that still
functions the same but looks like a modem to windows.
This way, OpenVPN would look to Windows like a Dial-Up connection
and could also be used to log on to domains using the "Log on using
dial up connection" checkbox at the logon prompt.
However, this setup would require this "modem driver" to implement
a completely functional TAP32 interface. Probably there would also
be some OpenVPN code that would have to be changed.
Maybe this here makes things clearer:
What I have in mind:
I'm not saying the TAP32 adapter should be replaced, but in some
setup scenarios (like road warriors who need to log on to a domain)
a modem driver based implementation would be easier.