As this is a old issue I think needs a mention time to time and 2 ideas -1 well known- came to my mind.
One is Merge teams of higher levels and do a combination of 9 Leagues of 14 teams to create like a bubble of teams, lets say of same level, the 50 as example, that, should always promote all together, the 14 teams x9, and allow the creation of 2 cups and 4CLs/SLs, adding few bots to complete the rounds.
With this teams aren't stuck.
The 2nd option is take into consideration the server flexibitity and distance between the L1-Max L and, promote practically entirely the leagues at L1, one time every few seasons, so it would work as a worm crawling, leaving free space in the last L1 for new teams + bots that could work as a new server opened.
I think this could save space in the 50% of the +200 servers we actually have really... still not sure about the capability to suport X amount of teams per server in which case still so valid the point to, have a server where the Min. L is the L1,
But other servers can eliminate the L1 and promote the lower level entirely from X level... so, moving all L40's-50's in a same server and doing this.. like expand to L40-51, 40-52... 40-53 and then promoting 40 to 41 as min level, this well done, allow a proportional promotion inside X-Y levels that could be aconstant distance.