Hmmm... You should rethink your design IMHO.
There is a solution for this, but you'd have to manage your IP Addressing with MT IP Pools (Which I don't particularly like when I'm using Radius).
Create a IP Pool, use the PPP Profile for your dialups.
Read the MT Documentation about I believe, Framed-IP-Address. I haven't checked the docs myself - feel free to do so, but I believe you can tell the MT which PPP Profile to use for Address management via Radius. Then your Local-Address will be picked up from the PPP Profile, as would your remote IP, but your problem should be solved.
From the MT Docs (
http://www.mikrotik.com/docs/ros/2.9/guide/aaa_radius)
[qoute]
Framed-Pool - IP pool name (on the router) from which to get IP address for the client. If specified, overrides Framed-IP-Address
[/qoute]
Thats basically what you need to use, instead of Radius Managing the IP Addresses via Framed-IP-Address.
Cheers.