I want to see players receiving enough money so that the bar is at a reasonable standard for enough players to be able to earn enough to pay their way on the tour each year.
You want a situation where there are enough players able to make a living to keep the lower ranks competitive, but to allow the talent to rise to the top on the basis of their abilities, not on the basis of their ability to get financial help to keep them going because the challengers do not pay enough for them to break even, let alone make money. It's not healthy for the sport if too many drop out because they can't afford to give themselves a decent shot at making it. If prize money distribution was geared so that, say, the top 200, 250 can break even and perhaps make a small profit after expenses from a decently full schedule, it would be better for the long term health of the sport.
Otherwise what you have is tennis continues to be a rich persons' sport - one where most of the guys who exist outside the top 100 are only able to do so because of their own private or family wealth, some sort of sponsorship, or financial assistance from the national federation. None of these are ideal.
Oh, I completely agree. I just don't want to see players receive too much money because they lose in the early rounds of the GSs. Ideally tournaments from below will receive more financial support from the ATP and some of that can come from the Slams.
As you said, increasing the level of challengers/futures will increase the overall level of the sport and the ATP will find it easier to find more stars.