You could coat-gelatin or poly-D-lysine or mixture of both by simply stand-still for 1 hour, dry, wash with ddH2O, complete drying in air. This is for cell culture substarte.
You are certainly right - the scheme you proposed will work.
However we need to modify the Teflon substrate in that way that - the modified outer layer - to withstand rater high Temperatures (say 180-200C - would be what we need.