Hmmm...MacNicol does look hobbity and a bit like Bilbo

. But I have 2 reservations. One is; can he do a
good British accent? This is very important. I can't remember seeing him in anything where he does a British accent (didn't he do a wacky Eastern European accent in one of the Ghostbuster movies). And two; he's roughly 55 which is the right age for book Bilbo (and technically film Bilbo too), but judging by film Frodo Hobbits can maintain their youthful good looks until their early 50s

. So I think PJ and Del Toro will be looking for someone a bit younger.
I wish they would actually use Sir Ian Holm. Surely nowadays the digital technology exists to de-age him

. But fat chance of that happening. Barring that, Colm Meaney (who is also in his mid-50s) would actually be ideal for the part. He looks like a hobbit, looks very Bilboish, has an Irish accent and is also the correct age. But, again, they are more likely to go for someone younger, like Ewan McGregor (who would be quite good if they put a bit of fat on him).
Gandalf's Beard