You can always make a soft print or scanned image from a sharp negative, but not so much the other way. I'd go with the Big 4 lists of sharp lenses above, and I'd agree that 210 mm is a good focal length for portraits; I certainly wouldn't shoot that subject matter with the 135 mm that lives on my Speed Graphic (unless I was out street shooting and didn't have another lens).
One nice option here is a 135 or 150 mm convertible lens. These won't be cheap and tend to be slow (f/8, perhaps, instead of f/5.6), but you get, in effect, three lenses for the price of one. The complete lens gives you the primary focal length -- say, 150 mm, nice for general use. Take off the front lens group (just unscrews from the shutter) and you get a ~265 mm lens 2/3 stop slower -- almost all 4x5 cameras have enough bellows draw for this length, and while it's longer than 210, it's still very usable for portraits. Unscrew the rear group and put the front set in its place, and you get a third, still longer focal length (in the above example, it would be about 345 mm -- which is a little long for some 4x5 cameras, but very usable for others). But you only have to pay for and haul around one lens and one shutter to have those three focal lengths.