Heidenhain TNC145 - drip feed

Hi there.

I'm looking at buy a Bridgeport Interact Series 1 CNC Milling Machine, which has Heidenhain TNC145 control. Firstly, am I correct in thinking that this can not be drip fed via serial so I'm stuck with the 1000 line limit??

I really would like this controlled via serial, so what is the cheapest option on upgrading, / modifying the controller, can I simply swap it out with a 155 unit?

Any help or advice would me magic.

Thanks

Jim