Here's another idea for you - you could use the main tuning control for
"rough" tuning, then use push button control to move the frequency up or
down one lock point. E.g. if you have lock points 10Hz apart, you could
arrange for two push buttons, to increase or decrease the frequency by 10Hz.
In this case "all" that is required is for this function is that pushing a
button delivers a sufficient pulse to the integrator to move the VFO
frequency past the half-way point to the next lock point. The stabiliser
will then move you the remaining couple of Hz to the next lock point.

I have not tried this and I imagine it would need to be adjusted carefully
to cause it to jump only precisely one step. Linearity of the integrator and
tuning voltage resp. freq would also need to be reasonably good. But I do
feel that it would work well: the applied pulse needs in theory to move the
VFO (in my example) by anywhere between 5 and 15Hz, and the stabiliser will
act to bring it back to the desired 10Hz move.

That could be quite a nice feature in your case, if you find that you want
to move 10Hz (or whatever lock distance you choose), just to move some QRM
outside the IF passband.

Huff Puff circuits are a lot of fun: a simple circuit with endless variety
and possibility for experimentation. DDS is a little more complex and also
poses the risk of spurs, though as others have mentioned their effects can
be mitigated.

73 Hans G0UPL
http://www.HansSummers.com