Currently, a private region allows 20,000 land impact, and you can pay x amount of money a month to get 10,000 more land impact, which is great. However, I know that some large busy sims that are at 29k and in a constant state of prim crisis. In these sims, we're stifled when it comes to not being able to do temporary event builds and other innovation.
I stopped by the official Welcome Hub and noticed that it's got 45k land impact used and a 58k total land impact. What this says is that it's possible to go higher.
So I'm suggesting allowing users who have already upgraded to 30k and are actually using at least 25k of it be able to purchase an additional 10k. By making it this way, people will still want to be efficient because money is money, but, give them the ability to get some breathing room if they feel they need it enough to spend the extra money.