Hi William, again!
I've been this way a couple of times, both times I had the north shore of Loch Mullardoch as my FWA, although I never did it. I think it's a long hard trudge, with some tricky river crossings where you might have to climb quite a way up if there are no handy surprise bridges (there never are...), but if the weather really is so bad you can't do the bealach, there isn't much alternative.
I stayed at Iron Lodge the first time as it was open, but a disused estate cottage rather than a bothy of any kind. There was a water tap outside.
The second time I camped above the zigzag path before Loch an Droma, which was where Ian Cotterill was camped I think.
The walking is not at all bad until after you cross the Choilich - the river is wide! About knee deep (I don't have long legs though...) and I did it the first time in awful conditions. It was okay, but be sensible. The stalkers path is mostly good, I found it harder to follow the first time in really wet, sleety conditions, easier second time. Really lovely glen, thoroughly enjoyed it.
First time:
https://gemini-challenge.blogspot.co.uk/p/the-planned-route-plockton-to-lunan-i.html?m=0
Second:
https://gemini-challenge.blogspot.co.uk/p/the-great-outdoors-challenge-2015-oban_12.html?m=0

Hope that helps. Enjoy! 😊

Thanks Louise

Unless the weather is really terrible I will go over the Bealach. But I am sure that we will have sunny weather for the first week ! .

William