Hi,
Not much we can do about it without making our own ASIC tough :p
Getting a modem to work at all would be the first step anyway, then optimize for size and cost, ideally of course reusing cheap hardware already on the market.
I don't think it's that hard given we have working examples.
TX is easy. RX is already implemented in RX
The main part is having properly timed TX/RX.
Sylvain