No idea what is Biometar rendering. However, for great portraits I would never use 50mm equivalent, that always ends up ugly.
I’d definitely use a TeleRolleiflex with a Rolleinar. This will take care of the model’s face and features while adding boke to the image, because you will be closer.
There’s definitely some magic happening with a Rolleinar.
Your pockets must be very deep...
A nice choice, if you can afford a Tele. Also, if you can find one in usable condition - most I've seen in recent years have separation problems in the taking lens, which will cost an additional small fortune to have fixed.
The Rolleinars for this beast are a design unique to the Tele and will also cost you a small mint, again if you can locate one or the two. The last set I saw up for sale would have cost almost as much as the camera. Of course nobody bought it and eventually the listing (on Ebay) was pulled. The regular two-part Rolleinars are cheaper, but their prices are also way up nowadays.
Another "minus" with the Tele are that alas, they are the most expensive (along with the Wide Angle Rollei) to repair. Parts for either are scarce (and expensive) as not many were produced in their time. Yes, new models are, or at least were available from Rollei in Europe, again at a super high price.
Nice try. Something maybe more, well, realistically affordable? With a little care, a "regular" Rollei TLR or any other TLR (Yashica comes to mind) in good condition, will give you exceptionally good portraits, if you can resist sticking it up the subject's nose and keep a little distance between you and the sitter. Then enlarge a little.
They are also much more easily found and purchased in reasonable working order. Plus repairs if and when needed are expensive, but not as much as the rarer models.
So it's best to buy a standard Rollei, ideally one from the 1960s (many Ts are available in good working order) and learn to use it well.
Problem solved!!