If you need to maintain the sine output, then my logic idea is no good. Better just to use some high frequency op amps or RF gain blocks with high output/input isolation.
Another point worth mentioning is to insure there is no RF noise or feedback radiating back into your oscillator from external sources. Perhaps some RF bypass capacitors on the wiring inputs would be helpful. Also, keep magnetic noise sources like switching regulators away from the output circuitry. You have to be pretty fussy to achieve 0.1 ppb.