A FT TC4 and a TC4 with the BMI chassis may be comparable in price if you are comparing used equipment. If you are comparing new stuff, the FT TC4 is going to be much cheaper. Especially considering all the hop-ups that come with the FT that wouldn't come with the regular TC4.
Honestly, I would go with the FT TC4 to start with. Then when BMI makes a chassis for the FT, you may want to get that depending on what the differences are with the BMI chassis.