I like the idea of having 5-5.5 mhz VFO (for all bands) mixed with band
crystal.
Lets take 40m band as an example:

I still must provide 15mhz to mixer (15 LO - 7 RF = 8 IF). Right?!

Now - how to produce 15 mhz from 5 mhz VFO and band crystal osc?
Obviously I need to add another mixer and feed its input ports with 5
mhz from VFO and 10 mhz from crystal osc. This new mixer would have 15
and 5 mhz at its output. Right?

Now..how to block 5 mhz and let 15 mhz go through towards my existing
RF/VFO mixer?

Obviously low-pass is not an option here..

thanks guys!