Unless you are doing a coupled approach in which case you will never get GS capture.
I think intercepting the GS from above is dodgy.
Intercepting the GP from above is the norm at larger airports where CDAs are expected to be flown by just about anything that makes a bit of noise.
Possibly irrelevant to TB20 ops but, given intercepts from above happen hundreds/thousands of times every day, it mustn't be too dodgy.