Cheap singlespeed cyclocross conversion

Just a thought... I've not done it but if you run double rings up front (with no front mech) you don't need to unbolt the rear wheel to change gear, you have a straight chain a all times and bigger difference in ratios.

You could run a 34+36 up front and 18+16 at the back. This would give you;

34x18 = 51 gear inches
36x16 = 61 gear inches

All without moving the wheel or a chain tensioner.

I dont think a double up front and a double at the back would be not sensible, why not have gears? Chainline would be a bit messy and I think chain length changes like that I think it would be hard to get the same chain in those dropouts.
But I do think two cogs at the back is a practical idea with 1 or 2 tooth differances