Whether or not you decide to use boots, I would recommend getting a good rasp (I use a Belotta) and learning how to maintain your horse's hooves in between trimmings anyway. It's a great skill to have if your horse gets a chip or something and you want to clean it up without having the trimmer come out. I've actually rasped a horse for someone at my barn when her feet were cracking because it seemed the previous owner never had a trimmer out. Granted, that was mostly just to help her be a little more comfortable until the trimmer could get there, but it's comforting to now I can do basic care of my horses' feet. It's also forced me to learn more about their feet and why they're that way, and I know what I'm looking for when it comes to signs of trouble, especially since I take a good look at their feet frequently and know what's "normal"
And it's super simple to learn!
As for the weakening of the hoof, I'd ask your farrier. He seems like he'd give you an honest answer since he's not a "need shoes" type of farrier.