See below for the poll, you can vote for multiple options as most are not mutually exclusive, but try not to vote for each of the few that are :)
I've included a little discussion on the options in the poll below it if you want to better understand what you are voting for.
Presently National limits the below level players at 50%, but some sections have a lower limit and apparently some a higher one. Reducing it further could be either a lower percentage or a fixed number, say three, like is done for above level players in plus leagues.
There presently is no limit on how many below level players can be in a given line-up. If they are on the roster, they can be in the line-up. Limiting this would probably be a fixed number like two or three.
Presently a below level player can play on any court and captains can use this to "throw" a match on court 1 while putting stronger players on 2 or 3 to try to win the team match. Limiting below level players to only play on court 3 then 2 would be similar to plus leagues where above level players must play on court 1.
You can vote for both a limit the having to play higher numbered courts to combine them and you'd have a situation where you could play two below level players, but they'd have to be both on court 3 doubles or one on court 3 doubles and one court 2 singles. This again is like what is done for plus leagues.
The playing up problem is particularly bad in plus leagues where you can have a 5.0 playing a 4.0 on court 1. Adopting one or more other options can partially address this, but one could also just not allow playing up in plus leagues at all.
Presently, a team that goes to Nationals must split up (no more than 3 from the same roster on a team at the same level) or move-up. When they move up, the 50% roster limit is waived so they can have as many playing up as they want. This only affects a handful of teams, but perhaps it should be eliminated.
If you have another idea, write it in!