It depends upon the price difference. Since the rig I imagined had a
digital synthesizer as its signal source, it would have to be "pulled" to
transmit. In plain English if you used a 455kHz IF (as cheap components
are available for it), you would have to have it shift the synthesizer
frequency 455kHz when you keyed the transmitter.
If you have a 455 kHz IF, for SSB you'll need a 455 kHz or thereabouts
BFO. If that BFO were a digitally synthesized affair, it would not be a
big deal to have it operate at a second frequency for CW transmit. It is
quite common for rigs these days to have their transmit signal, in every
mode the rig is capable of, generated at the same frequency as the
receive IF frequency (you're going to have to do this for a SSB
transmitter using a balanced modulator and sideband selecting filter
anyway) and then heterodyne converted to the operating frequency. For
the sideband selecting filter it is probably cheaper and more effective
to use crystal filters and IF frequencies much higher than 455 kHz.
That's why Drake, Heathkit, Kenwood, Yaesu, Icom, Ten-Tec and others do
it that way.
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