Hi
Untill you have enough memory and CPU to handle the dynamic VPN Sessions there shuldnt be any problem .
Basically u would be requiring the appropiate IOS to support the dynamic vpn clients and of course with enough RAM/Flash to support the IOS.
If you have all these in place u can get that done in ur box.We had the same kinda of setup but in a 2611 router with enough RAM/Flash to support the ios and other stuffs.
regds
prem