Why not have wig-wags AND “Normal” traffic lights? They could be sited a little distance back from the crossing barrier, complete with the normal stop-line on the road surface and any other “Normal” features. This is the right set of visual cues for a road user, it means STOP in no uncertain terms. And it should be easy to do, the traffic lights triggered to red by the initial yellow of the wig-wag, and cleared to green as soon as the wig-wags stop.
As an aside, (I hope you'll allow it, oh Mods) is it 'amber' or 'yellow'? Here railway usage meets road usage. The wig-wag reds are preceded by – what? The colour is plainly yellow in both regimes, yet the Highway Code persists in this use of the word 'amber'. Amber is a substance, it is fossilised tree resin. Yellow is the colour. We could extend this use of the names of 'stuff' to describe railway signals “ - as I came round the curve I saw that the signal was blood, but it immediately cleared to grass with out the intervening amber”. How crazy is that?
A route indicating "feather" could be "Snow".