"But I also like longish sequence DSSS as a carrier mechanisum due to the fact it plays much more nicely in places like the HF band or even in "white space"..."
Hmmm I'm not sure that I agree, wide band HF comms is typically limited by multipath fading rather than noise floors, so it is exactly these frequencie bands that benefit the most from OFDM techniques.
The typical problem with DSSS is the ISI (inter symbol interference) caused by multipath. to make it very wide band you need to equalize the signal across the entire band, which btw is dynamically changing. Anyway this is definitely OT so I'll leave it.
PS To prototype HF systems is very easy these days. Anyone can buy 14 bit 200Mhz ADC's and DAC's, off the shelf, (ADI, LTC, TI..) with a little work there is no problem interlacing these COTs parts to make a 14bit 1Gsps ADC / DAC. This analog block makes HF radio very easy.
Single FPGA's are definitely big enough, these days, to fit an entire OFDM / FEC system Mod/Demod and digital interface. So all you need is the external DSP and you can make some very nice bespoke HF comms systems .
The older FPGA prototype boards can be easily purchased on Ebay for a few hundred, plus Octave is just as good as Matlab for many of these comms apps. Development costs should not be big factor in prototyping HF systems, no more than maybe $2K.
Anyway, you really need to get back into the game because the young guys are all digital comms hacks and have never known the old school HF design methods. There is a lot of value in combining old school knowledge with new technology!
Actually CSIRO has a HF DIDO development project just started, its a bit hush hush but I'm sure you can find the details.