That's a problem, and that's why mainland or commercial private sims are messy, laggy and with a lot of problems.
Of course LL give anyone who owns land the possibility to do what they want, and that's surely a nice thing, but for the ones like you, living in such a sim can be crappy.
As you own half a sim there i would ponder to get in your own sim, maybe find some friends who will share with you the other half.
And i don't think LL can or will do anything about that.
The idea of a % depending on the parcel size is interesting, but not in that way (someone who owns a 512 parcel should enter with just half their body *giggles*).
Maybe it could work something more cmplicated, like depending on how many parcels owners are on their land at any time, adjust the % that way.. so that if the only parcels owner in your sim will be that 3k parcel owner, it is right that he might have 100% of ppl, why not. When you get on your land too, so there will be 2 parcel owners, then a percentage might calculate the total land "used" in that moment (32k + 3k = 35k) and share ppl that way. So that his 3k would be "more" than 3k.. But then other problems will hit in, say other parcels owners get in and the sim is full, should the system "kick" out ppl to allow new comers to get in? Hmmm wouldn't work.
Maybe a good thing could be leaving a minimum of ppl for each parcel depending on the size. like 1/2 of the total allowed... so if a sim supports 60 ppl, 30 ppl should be "set" to each parcel depending on the size. The ther 30 "free". You own half a sim, so that would guarantee a minimum of 15 ppl all the times in your parcel. The 3k owner will have 2-3 (2.5) minimum ppl who can get there at any moment. Both of you will have the other 30 allowed ppl on the sim to be where they want, so during club events he might even get them all (30 + his 2) but you still will have your 15 allowed just to your parcel.
The problem is: these numbers work for a sim that supports 60 people and for parcels bigger than 2k (smaller parcels like 1k or 512 wouldn't get a single minimum allowed.
Maybe a mix of the above thoughts (yes i'm just thinkin aloud) might work who knows..
My tip is still: get your own private island, and if you can't afford the whole share a half of it with some friends and live in peace
