Do you like to shoot outdoors, or uber-complicated setups indoors? If I know you at all, it's the former, which means DO NOT BUY A MONORAIL. You want a field camera. Yes it costs 4x as much, but there is no way I could imagine lugging any of the monorails that I've tried around outside on a good walk. Then again, if you only plan to shoot wetplate, you'll probably be right next door to your darkroom/lab and a cheap monorail that you can drip nasty liquids inside is a good option.
If you like slightly-wide normals, get a 150. If you like slightly-long, get a 210. I personally have a 150 and would prefer that it was a 180, but that's probably because I spend so much time with the 110mm on 6x7. I have a 240, and it's too short for a "long" lens for me so I think I need a 360. 90 is nice; going wider than 90 usually means bag-bellows and insufficient coverage for movements unless you spend $10
3+.
If you like long lenses and/or high magnifications (a close headshot is more than 0.5x magnification!), check the bellows length. My 45A barely does 300mm and that's very limiting. Some cameras have interchangeable bellows. If you want to shoot 65mm, you probably want some means of putting a bag bellows on because recessed lens boards totally suck (you can't reach the controls, sometimes need special right-angle adapters for the release cable, and tilting/swinging causes shifts).
Try to get one with a Graflok back so that you can put rollfilm holders on it. Why modified sheet holders? Get at least a handful of normal ones and use them to practise with the camera and some cheap (Arista) film before trying the super-difficult approach. Being confident in the camera means less things to worry about when you start on the wetplate - know that your bellows are light tight, apertures and speeds are accurate, GG is correctly aligned, etc, etc.
For the wetplate, which I understand is a super-slow emulsion, I would be tempted to drop a small quantity of cash on one of Reinhold's homemade meniscus lenses. I think they're around f/3.5 or so depending on focal length and very cheap. No shutter, but that's what your velvet-lined top hat is for
