Home-made, from scratch
Thanks for the information. I've been checking into Tx modules, and found one for $44. Then like you said, I could reverse engineer a standard receiver to get my signal back. With an oscilloscope I should be able to find what I need on the boards. If I can get used equipment I think I might go for it. Otherwise, it doesn't make a lot of financial sense right now.
About the data- I can use either UART and write a packet communication protocol with serial data and headers, sync bits, and so on. Or I can use serializer / deserializer chips from Holtek built specifically for the purpose of RF communication. I'm leaning towards Holtek because UART logic levels don't cope with RF noise very well.
I don't think I'll be sending as much data as you think. If I send at 2400 bits per second, each packet of data is 50 bits long, and all four control channels change at once, I'm still only sending 200 bits, and I can do it 12 times a second to saturate the channel. By not continuously sending data the FCC means they don't want you sending data such as from telemetry or applications using continuous feedback.