If it was up to me, and if I was the pastor of a church, I would probably have see-through grates installed with small velvetish curtains on the priest’s side in front of them. They would be closed for anonymous confession by default and if the penitent wanted to confess face-to-face, he could say so and the curtains would be pushed back. I would also require completely separate entrances for both priest and penitent leading into the confessional. This allows either style, while physically preventing accusations as much as possible in either case. This would also allow for the possibility of the priest being able to refuse face-to-face confessions, as is his right, if he judges it necessary or if he wants it.
This is a pretty simple solution that can be installed quite easily in most existing “box” style confessionals, but it might pose a problem for the silly “reconciliation room” set-up. Disregarding the psychological implications of anonymous vs. face-to-face confession, I think this is the best and most common-sense approach, which is of course why it probably doesn’t exist. (just kidding)
With box-style confessionals, a reasonably well-bodied priest can install this or can have a parishioner do it in less than an hour for very little money. Personally I view this from the perspective of protecting the priest and the penitent and I see it as quite imperative and such an easy thing to fix.