I think the best way to get the most money is to grow the league and keep it on top. Parity helps with that. 18 games would help with that. Revenue sharing helps with that. The NFL has been so successful it seems in large part because they put growing the league in front of all else. That and the product rocks.
If they want to do away with the cap, I think a tax system like basketball would be effective at giving a couple teams a slight edge while still maintaining parity. They could also make the 5th year unrestricted instead of the 4th to keep players with their teams longer and give them more time to work out deals.
I do think having the most popular teams in it a little more than the others is good for the league too. Cinnci probably has 1/10 or less of the fans Dallas has. The NFL benefits when Dallas is good.
0.01-5.00% over cap = 30% tax on anything over
5.01-10.00% over cap= 50% tax . . . .
10.01-15.00% over cap = 70% tax
15.01 - 20.00% over cap = 100%
20.01 - 25.00% over cap = 200%
25.01 - 30.00% over cap = 300%
30.00 - 40.00% over cap = 400%
40 - 50 = 500%
I think this would allow for the teams with the most money (fans) to spend slightly more, keeping the NFL more interesting to more people, but not so drastically unfair that the small teams can't be in it every year too if they have a good GM and coach leading the way.
Baseball has one team spending 30 mil and another spending 300 mil. Comparing that to my proposal, you'd probably see the smallest teams around 100 mil with the cap at 150 mil and the largest teams at 180 mil. Small teams win in baseball against a much wider gap in spending. This would keep parity, but also have more fans interested more often.
If my main goal is growing the league (money pot), this would be my proposal.