Using the transverter approach offers the advantage of providing a higher-stability signal generated by the main station's transceiver oscillator system. Most of the digital modes require a higher stability than would be needed for straight CW.
If your main interest is normal speed CW, then a digital VFO, such as the one devised by GW3UEP, would do the job.
If you are content operating on 475.0 kHz, then an inexpensive 7.6MHz crystal, in a divided-down oscillator will work well, and with good enough stability for some QRSS work as my earlier "GW3UEP Transmitter In QRSS Mode" report indicated.
The other option for frequency generation is a DDS.
For those wanting something a bit more robust, W1VD describes a very nice high-power transmitter. His website is packed with useful circuits and ideas for both 2200m and 630m.
|W1VD Dual-Band Kilowatt : http://www.w1vd.com/|
|Homebrew 630m two-Port Power Combiner / VE7SL|