I'm fine with rules heavy splat books as long as they are big discrete packages that are easily browsed. I'd rather not have tiny fiddly bits (I'm looking at you, feats) spread across multiple books for the same character concept. So I dont want to consult 5 different books and 12 Dragon articles to see the options for making a wizard.
Now DDI gives me access to this stuff, but not in easily browsed format. It's searchable but you have to know what you're looking for. So eg if you don't meet the prerequisite's for a feat you won't see it.
I think the optimal number might be 3: a PHB, a mechanical module book, and a setting book. In fact, that doesn't sound like a bad house rule.
Alternatively, they could utilize the concept of modules + POD to let me generate my own Splatbook. That way you get the material but in usable book format.