I don't think YABU, but I may be biased, based on my own recent experience! My DSis is getting married later this year and I, along with 3 other adult Bridemaids, was tasked with arranging the Hen. My DSis is a very popular lady, so there were around 45 women on the initial invite list and she asked for a weekend do, so it was a pretty big event to plan!
We ended up with 35 ladies for the weekend and due to the wedding being postponed from last year to this, for obvious reasons, it was nearly 18 months in the planning. It was a huge undertaking - simply finding a venue which could sleep 35 of us and where we would be the sole occupants for the weekend, was an enormous task in itself. I must have sent hundreds of emails to various suppliers (DJs, venues, caterers etc.), many more to the Hens and our BM's Hen Weekend Planning Whatsapp group must have around 10,000 messages in it!
However, depending on how many you plan to invite, as long as you can secure somewhere suitable to stay (the good places get booked up very early) and you can let them all know which dates they need to be free, then in reality, those planning the Hen don't need to do terribly much with 6 months to go (assuming you'll have the Hen shortly before the actual wedding?) I would have a word with your BMs and get them to confirm the dates and location, make sure they have a guest list and contact details for all the invitees, then let them run with it - you should just be able to turn up and relax, in my opinion it's definitely a BM job - the Bride has plenty to do!
Just for balance - when I got married, nearly 20 years ago, 8 of us went for manicures and facials, stopped off at a nice bar for a glass of pink champagne, had a delicious meal at my favourite restaurant, then I drove myself home and was in bed before 11 - and I organised it all myself! Whatever you end up doing, I hope you have a fabulous Hen and a wonderful wedding!