PDP-11s are a type of computer (to be exact, I should say they are an architecture). They are not built to run a modern system. Look at the architecture, look at the word length, look at the address space: 16bit registers, 64K address space (can be doubled starting on the 11/45 by doing I/D split), FPU not built in (instead it is a peripheral that's accessed as IO), physical memory limitation to 22bits of address space. I've used various PDPs (mostly the 11/55 model, because it had good bus bandwidth with the Unibus and a reasonably fast CPU), and an LSI-11 (which by modern standards is dreadfully slow, but in the 80s was a good laboratory instrumentation control machine).
SystemV is not a computer. It is a flavor of Unix. Grammatically correct would be to say: It was a flavor of Unix, since I don't know whether it is sold any longer; that's all the complicated story of Novell, USL, SCO, and so on. To my knowledge, no pure SVR4 is sold today, although some commercial Unixes (AIX, HP-UX, ...) may still contain licensed source code from it.
The idea of running FreeBSD on System V is just wrong. It's like saying you want to drive a Ford on a Chevy. It makes no sense. And the idea of running a modern Unix-style OS on a PDP-11 like saying that you want to build a modern passenger car, but using the engine from a bicycle.
I'm sorry to be blunt, but your post seemed to be mostly confused word salad.
(Side remark: A friend of mine has a PDP-15 and a PDP-8 at home in the garage; the PDP-15 is fully functional, and last time I visited, the PDP-8 was down for maintenance. I don't know anyone who has a PDP-11 that still works, but most likely those exist.)