There is no reason NOT to use enlarging lenses for portraits or other types of photography as long as you are happy with the rendering you get from your chosen lens. I regularly use various enlarging lenses on a 5D2 for portraits and also for the equivalent of 'product' shots.
Setup used on the 5D2, Meogon 80/2.8
I've found most enlarging lenses to have a broadly similar rendering in that they tend to have a harsh bokeh but I try to use this to my advantage. I'm yet to find one specifically with a soft bokeh, of the 20 or so enlarging lenses I've used.
I like the Schneider Xenotar 80/2.8 and the Meogon 80/2.8 for portraits, but there are lots of inexpensive gems out there. I also like the Ross Resolux 110/4, Taylor Hobson (TTH) Ental 5" F4.5 or the Schneider Componon-s lenses in the 100-135 range. The biggest problem with enlarging lenses is that some times it costs more for the adapter than the lens. I have had several custom adapters made for lenses such as the Xenotar and the TTH 5". Most of the US made lenses also have unusual threads so are generally in the 'too-hard' basket as far as I'm concerned.
Re the Zoerk adapter, if you are limited to a longer lens then so be it. There are still lots of options out there. There are lots of high end enlarging lenses too, such as the APO's from various makers, but these can be very expensive.
I also use a NIkon PB-4 for tilt/shift on a 5D2
I've
compared a bunch of 100mm+ lenses with significant amounts of tilt, using the PB-4 bellows above, and this might be of some help to you.
JJ