And extending the idea of playoffs into promotion relegation.
Because BB only promotes 1/16 teams and relegates 1/4, there are going to be a lot of bots in the upper divisions. But because BB doesn't have qualification matches between divisions, it is relatively straightforward to promote additional active teams into the upper divisions to replace the bots. This is unlike the case of HT, where the problems with the re-organization were in part due to it being done after conventionsal pro/rel, so you had teams bouncing back after relegation.
So the basic principles:
(1) No team can promote more than one division.
(2) Bots can relegate several series if possible.
(3) The division playoff champions promote, it they have an owner. If there are any bots that win the playoffs they simply remain in place where they are.
(4) Additional active teams can promote if there are bots in the upper division that they can replace.
After the playoffs, start with top pair of divisions, which will be referred to as the upper and lower division.
Count number of bots in upper division, nub
Count number of active playoff champions in lower division, nlpc
Count number of active teams in lower division, nla
Determine number of teams to swap: We'd like to relegate all bots if we have active teams to replace them with, plus we want to make sure that the active playoff champions promote, even if it means relegating active teams:
nswap = max( nlpc, min( nub, nla ) )
And the number of bot and active teams that relegate, nubr and nuar
nubr = min ( nswap, nub )
nuar = nswap - nubr
Figure out the teams to swap and execute swap. If bots are being relegated, it doesn't matter which are relegated. If active teams are being relegated, I would rank them on the basis of fewest wins under the current owner, including playoffs; lowest winning percentage (0-0 is lowest possible). I would use league place as a lower tiebreaker than games won. Also care should be made that active teams that have already relegated rank above all the other active teams (ie division played in, is actually the first criteria). Similarly, the teams to promoted are ranked on (1) whether they are a playoff champion; (2) most wins under the current owner, including playoffs; highest winning percentage (0-0 is lowest possible). I would also use league place as a lower tiebreaker.
Swap the teams.
Repeat the process for succeeding pairs of divisions.
Note that the above handles some special situations, without modifying the algorithm:
Bottom division all bots: Both nlpc and nla will be 0, which will make nswap 0.
Upper division all bots. Let's say that we are dealing with D.II and D.III, so nub = 64, then the top 64 active teams in D.III will promote to D.II. If there are fewer active teams in D.III, all will promote. BB could place all new teams in the bottom division, and simply let them race to the top over a few seasons.
Bottom division just a few filled series. Assuming bots in the 2nd bottom division, then a relatively large percentage of teams in the bottom division will promote, but unlike HT, active teams won't be flung across the bottom division to play solitaire.
When new owners are assigned, they should start with a 0-0 record, and teams should be ranked in the conference on the basis of most wins, before winning percentage. Bots should slide to the bottom of the standings. So if someone enters late in the season, they will have relatively little chance of promoting, unless they are the playoff champion.
To promote, a team should (1) strive to win the playoffs for their league; (2) win as many games as possible.