Well, first, I'd say it's too late to make any changes for the 2009 season. People who played 2008 based on the expected 2009 rules (and thus built teams to maximize your settings) will be a bit reactionary about any changes. If you say that you are looking to discuss changes for the 2010 season - and have them all settled before the draft - people may be more engaged. Plus it'll give you something to do before the draft.
First thing that I think keeps the league fresh is to put a limit on the # of years a player can be kept. If there's no limit, you're going to have a guy with Pujols, Hanley, Sizemore, etc for the next decade. Kind of boring. We have a limit of 4 years (or 5 years if we acquired them as minor leaguers)
Second, in terms of keeper types, the way we have it is round drafted + 3 each year. I drafted McLouth last year in the 20th round - he costs me a 17th round pick this year. Since it moves up 3 every year, the first 3 rounds (and really like the first 5 rounds) rarely have keepers (aside from guys like Lincecum and Braun who are being kept), so there is always a lot of talent in the draft.
You could reduce the number of keepers which makes it harder for someone to build a dynasty.
I disagree that you want to encourage people to "take a year off" and "rebuild". This results in one team selling off anything of value, and whichever team (or teams) trades away David Price and Matt Wieters for the other teams first 6 draft picks, it throws off the competitive balance of the league and ends up with a ton of people being pissed off.