I propose 3 tiers of rankings. Rank 1-32; 32-128 and 128- rest. Each Tier has a different set of mandatory events differing in number and rankings points.
Each Tier has a cutoff of rankings points. So the 32th ranked player has to have say, a 1000 points at least.
Tier I players have to play only certain 250, 500 and above mandatory events. That is, their tournament load throughout the year is lighter and skewed towards their performance at the bigger events. This is what the top guys want - more rest and less tournaments so they do better at the slams and Masters series.
Tier II players have to play more 250 level tournaments. They collect points by playing more tournaments.
Tier III have to slog it out the hard way.
The big difference is that once a player is in one of the tiers, they drop down into a lower tier or go up into a higher tier only 4 times a year. That way its not a continuous thing and rankings are "protected" within a short time span of 3 or so months.
How does this help? - well it effectively creates the separation that's really needed to address the different concerns of top players vs the rest. The lower ranked guys don't mind playing more tournaments to rack up points (and earn much needed cash). The higher ranked guys would rather concentrate on the bigger tournaments and have a lighter schedule. This way everyone gets to have what they want.
Of course at the slams, everyone in the top 128 have a chance to meet. (along with wildcards etc)
The tier system also rewards good performance and penalizes bad performance. So for example, if a rank 30 guy does not do well at the smaller load of higher point tournaments, (within a 2-3 month span), then they are pushed into Tier II at the end of that period and they have to play more tournies against lesser players to build their confidence and regain their ranking.
Similarly, someone who is rising in the ranks, once they are able to accumulate more than the cutoff for Tier I will get into Tier I at the end of a period and now have to play less tournaments but against quality guys at the more prestigious events.
Of course, this means fromt the POV of tournament organizers that the smaller events lose higher ranked players, but there is always appearance money. If Davydenko wants to play more events to accumulate cash, that's his choice. He cannot complain then that the season is too long.