Hi there- I am a builder and licensed mortgage officer. Generally, I think you may have some trouble with the FHA appraisal with this.
I would think it is well worth maybe $1000 total to add a 6 foot electric baseboard strip on its own T-stat in each BR. May need it for financing, but in any event any good buyer's home inspector or even the buyer themselves would question this anyhow. Its not a great system or condition for the potential buyer.
If you need anything, please let me know. Good luck,