For example:
Charge a fixed cost to register a domain
Make the amount of namecoins generated per block proportional to the block's difficulty (which is indirectly given by the total hashing power in the network)
Yes, the amount of generated coins is more or less static (halved every 200k blocks IIRC). But the cost of addresses is reduced every X blocks, where X << 200k, I don't recall what it is. Reducing costs with static generation or static costs with increased generation is the same thing, though your idea depends on difficulty in a way that the current system doesn't.
Regardless, I think that something like this would be hard to implement well, and it would definitely be a big step away from the bitcoin idea of limited supply. Because of this, I don't think we will see something like this implemented.
So if the demand for coins (or domain names) is higher then what is generated by the network, domains will be too costly, hindering adoption of the .bit zone. On the other hand, if there are too many coins that are generated, domains will be very cheap, leading to a large amount of domains being registered by squatters.
It is possible (I think) that domains might grow to be too expensive. But if domains are too expensive, demand should decrease thereby decreasing the price. This link might not work the way we want it to, domains might get too expensive for anyone but corporations to buy.
Being too cheap however should be adjusted by the free market, cheap domains -> more registrations. If squatting becomes a problem, the squatters will themselves increase the cost of domains by increasing demand.
So if the demand for namecoins is higher than what is currently generated, miners will be able to make quite some money by selling namecoins. Thus, new miners will be motivated to join the network, increasing the difficulty and thereby the amount of namecoins that is generated.
As for getting more miners, the miners will make the same amount of money whether they get many coins with a low price, or few coins with a high price.
Disclaimer: I am not an economist