Definitely not option 3. No point in buying another in-between car that you won't be arsed to run to work, and isn't focussed enough for track.
My opinion is:
Sell the 200 and 172, buy an Exige and daily the Mazda.
200 is a great all rounder, but isn't focussed enough for track and isn't (by your admission) comfy enough to nip around in. Sat on your drive it's loosing money, throwing money at making it a track weapon looses money and your warranty, and it'll still drop in value like a lead balloon. With the 200's I think you have to 'use it or lose it'.
An Exige (or similar) has the drama you want in a weekend car (but can still be driven on the roads reasonably) and is more than capable for track driving, also it probably wont lose value like the 200 will.