I assume horizontal 6 ft? Spouse vanity or someone else? Does it have to be a single piece? Is the bathroom vanity the primary place the individual will use to look at themselves or can you put something up somewhere else nearby that will negate the need for a gigantic bathroom vanity?
A huge one is kind of a pain in the ass. Depending on the user's approval, I wonder if you could get away with splitting it into multiple panels to be mounted side by side vs a single panel. This might fly especially if you go with something that has vanity lights built in.
It's kinda nuts. For instance on Home Depot, at 6 ft, you can get 72" x 80" mirror doors for like <$400. A 71" x 36" vanity can be between $1-2K easily.
40" x 36" LED vanities can be had for <$400 on a few websites. I'd honestly wonder if you can get two and put them side by side in a his/her type of arrangement for far cheaper. Also consider if you could downgrade it further if you install some sort of mirror nearby that can allow negate the needs of a gigantic vanity in the bathroom (ie: mirror door(s) or large mirror on wall somewhere).
I mean, a bathroom vanity isn't going to be great for full body review anyways. The sinks and cabinets get in the way. A 6 ft vertical mirror somewhere else would work far better. I think one idea I've seen was someone putting a mirror door on their shower.
ie:
https://www.faucetdirect.com/dreamli...glass/p3630097
Still though, I'd make sure the vanity was as big as possible within a budget you are comfortable with. I wouldn't pay $1-2K for a single 6 ft bathroom vanity. Within that same budget, I'd maybe consider a good value 4-5ft vanity and maybe a mirror door for the shower that is big enough for head to toe? Don't go too small for a bathroom vanity for a ensuite sized bathroom though (ie: <4ft). For a few hundred bucks difference, it horribly cheapens the look of the bathroom IMO no matter the trim level for the rest of the bathroom. I've seen it a few times in Air BnB.