There is no situation where it would be appropriate for Bellend to play. If St George had any brains they'd have already suspended him (with pay) and issued a statement saying he'll be focussing on his welfare blah blah and he'll be given as much time as needed so he can fully focus on dealing with the serious accusations.
This shouldn't even be a difficult decision to make really. As soon as you're dealing with something as serious as rape, being a decent player should immediately get thrown out the window and he should be stood down until it's resolved. The only issue in the past, like the Brett Stewart saga, was that he was suspended without pay. There was an implication that he was guilty, being suspended with pay, word it as looking after his welfare, I can't see any issues with that.