I think the slams have more than enough points now. If anything, they're too high. Just because the tennis media only pays attention to women's tennis 4 weeks out of the year (yes, I know the slams are 2 weeks, but the women get ignored in week 1) is no reason to change the system.
The slams are only as important as the players make them. If the players, as a whole, decide that these 4 events are the most important, they will be. If they don't (as in the mid-to-late 70's with RG and OZ), no amount of point-tinkering will change it. Back in the late 80's, with Graf, Navratilova, Evert, Mandlikova, et al, the slams all had prestige, despite awarding only 75% more points than a Tier II.
I favor going back to having the slams at no more than double a Tier I. Use that as a starting point, then adjust by prize money (not size of total purse, but relation to the men's purse). The formula would be PA= (W/M) * SP, where PA = "Points Awarded", W= size of women's purse, M= size of men's purse, and SP= points on the base scale. In other words, with OZ and the USO awarding equal money, the players would get the full amount of points on the scale. If one of the other slams awards the women 90% of what the men receive, the points given for that slam would be 90% of the initial scale. And so on. It won't change how the players perceive the slams' importance, but would send a message to the tournaments.