This is an interesting idea, but something about having various "behaviours" baked into the logic concerns me. I'm certain that Theo has thought about this and understands the implications better than I do though.
For example, if your process has TAME_GETPW opening /var/run/ypbind.lock enables TAME_INET. The reasoning behind this makes sense, but now it means that yp always has to open that file before it can do its thing. The behaviour of yp always opening that file before accessing the network is now required by the kernel.
The saving grace is that OpenBSD (and the other BSDs) are developed as a unified system, so if yp ever changes to no longer use that file, that change will only come as part of a version upgrade that includes the kernel, etc.
For example, if your process has TAME_GETPW opening /var/run/ypbind.lock enables TAME_INET. The reasoning behind this makes sense, but now it means that yp always has to open that file before it can do its thing. The behaviour of yp always opening that file before accessing the network is now required by the kernel.
The saving grace is that OpenBSD (and the other BSDs) are developed as a unified system, so if yp ever changes to no longer use that file, that change will only come as part of a version upgrade that includes the kernel, etc.