an example how maybe to work around the 14mz region lock I personally do not like at all:
You could use a FF8 or FF9 (a PLL module of the FF9 super would be best) and surround it by a DC/DC converter in order to get 10V for the transmitter module, a signal inverter using BC 547 and some passive parts (to block HF, resistors, ...).
The board is designed to carry the circuits, the FF8/9 module and use a shaped delrin part that connects the HF output to the 14MZ antenna connector. The PPM/PCM signale could be taken from the trainer plug, the power needs to be connected somehow to the LiIo battery of the transmitter.
The layout is basic and examples can be found anywhere in the internet, where inverters, DC/DC converters, ... are discussed. The pin layout of the 14mz HF connector can be evaluated by open it, the one of the FF8/9 transmitter module by measuring the output of a real FF8/9 radio. to the transmitter module.
Sure this is maybe not legal in all countries and it is just for test proposes.