Here is a view of the bike from the side.

What I am looking for in suggestions is.....
1. A way to mount a derailler onto the frame so that I can switch between the 2 cogs. I do not want the type of derailler mount that goes around the axle. Since this is a track type with the wheel sliding out to the rear, I am not sure that this is possible.

2. Option 2 would be simple with a chain tensioner and I could manually change the chain from small to large cog.
Ideally a 16 to 24 tooth change or there about for wider range. I live in VERY STEEP hilly country. My road has a 15 percent grade! And I would be happy with a 70 inch gear for the flats.

3. The clearance from the small outer cog to the seat stay is very close, so an upper mounted chain tensioner is out of the question. Some sort of lower chain stay mount might work.

4. Looking for suggestions on the gear cable setup as I am running drop bars so grip shifter is out of the question, and not sure if the old sturmey archer trigger shifters work on the larger road bar. Not many other places to mount a shifter. Maybe fabricate a tube bracket somewhere? I'm open to suggestions. On my CCM, I ran a super simple setup with a pulley on the seat tube and a quantrant shifter on the top tube for pure simplicity and it works great.