We walked this on a lovely October afternoon, after a long dry September and not all that much rain in October. This is relevant...

On the plus side, the alternative path is very well signed from the Ben Venue car park.

But...there are a couple of problems:
* First of all, the car park is now serving two popular hills, so be early if you want a space.
* Secondly, although they have done their best to get you over the wettest bits (with somewhat unsightly matting), the path is places is very steep, muddy/mossy and definitely slippery. And this after what has been a fairly long dry-ish spell... I suspect it will just get worse through the winter & spring, especially if we have a fair amount of rain.
* And I have a suspicion that the matting will become much more slippery too as mud/rain gets to it....

So overall, personally I'd say find another hill until the main path reopens. We met one or twofolk who were so unhappy with the conditions underfoot that they gave up. The only time it might be ok is in winter conditions so that everything is frozen! (in which case, don't forget the crampons, as it is steep in places).