what is "a good player" in BSS vs BSP vs L3 vs L2 vs L1 VS PL?

I have this sort of "rule", where I don't put anyone that gets at least a +7 score in my a-team. the score is calculated as follows: 11-15 gives 1p, 16+ gives 2p. obviously I will not follow this "rule" always, but as a general outline I use it. it works ok.

I am wondering though, what do you think is a "good player" on level x? and how much difference do you think there is between what constitutes a good player on level x as opposed to level y? how much better is a "good" BSP player, compared to a "good" BSN. I'm thinking about this in case I get promoted (fingers crossed), as I am wondering what will now be considered deadwood, and what new signings should I make. in essence: where to draw the limit?