From the "-P port" option reference at AVRDUDE: 2.2 Programmers accepting extended parameters
For programmers that attach to a serial port using some kind of higher level protocol (as opposed to bit-bang style programmers), port can be specified as net:host:port. In this case, instead of trying to open a local device, a TCP network connection to (TCP) port on host is established. The remote endpoint is assumed to be a terminal or console server that connects the network stream to a local serial port where the actual programmer has been attached to. The port is assumed to be properly configured, for example using a transparent 8-bit data connection without parity at 115200 Baud for a STK500.
This indicates that AVRDUDE, the program that Arduino IDE uses to upload to your Mini, does support doing what you want to do.