Why not integrate both systems???
On the T-VASI instead of 4 whites why not make it a normal PAPI, it would be an easy upgrade compared to changing to a whole new system, and you've got the best of both worlds. If you're slightly below appch path you'll get the usual 1 white 3 red aswell as the the white light below on the T-VASI...
in all situations a) you know you're below/or high, and b) you know how low/high, and where your predicted to land
Just a thought
