I also read through all of the Virtual Wire source, and it would not be hard to port the logic over to another language or app that was receiving signals.
The issue here is not the porting, but the fact that VirtualWire works at the bit level. If you connect a low cost RF receiver directly to USB/TTL you will only have access to bytes and anything you send from your Arduino(s) with RF transmitters will have to conform to USART/TTL (e.g. 8-bit, start/stop etc.).
Above said - I still think you may be able to get away without encoding for short to moderate range/speeds. Also you could improve your odds through implementing the parts of the VirtualWire protocol that work at the byte level (e.g. add a training sequence, use bytes with a favorable bit distribution, packetized data with checksum, send each sample multiple time for redundancy). Also use Hardware serial on the Arduino transmitters for more precise timing.
Hardware encoding is always an option, but will of course add to cost and complexity.