Wow, you are a planner! May 2010 is along ways away!
The thing with renting points is that it involves acertain amount of trust on both your part and the person you are renting from. For my own sake, that's not a risk I want to take when it comes to my vacation, and the amount of moeny that goes in to my vacataion. If you are comfortable with that kind of risk, then yes, you can save money.
From mousesavers.com:
"Renting points means you pay the DVC member directly (often by giving him a one-night deposit up front and paying the balance 30 days before the trip, though arrangements vary widely) and he makes a reservation in your name. The transaction requires trust on both sides.
I [ Mousavers' writer, Mary] have rented points on four occasions and in each case had no problems at all. In fact, for years I had never heard of anyone being ripped off in a DVC rental situation, but in 2006 I heard of some instances in which renters were the victims of fraud."
I suggest you read more on this subject using that site before you invest.
AS for splitting your stay, I have done that a number of times. My typical split is part offsite/part onsite. I do this when I want to visit the other Orlando. Last fall, we had an eight night stay booked at Pop, but I looked into airfare and an extra day early was so much less that it covered the cost of an extra night! Not only an extra night, but an extra night at AKL concierge level!!

Our package didn't start until the next day, so we consigned ourselves to a non-park day at teh beautiful resort. Another time we did a split between two rooms at AKL and two offsite condos (large group).
Okay, to finally address our inquiry (sorry for being so long winded).
The pluses are: first, gettingto enjoy two resorts.
The second plus, if you will, is saving money. Splitting a stay where one resort is expensive allows youto enjoy the amenities of that resort, without having to pay the extra for your entire tirp. The only way AKL concierge was worthwhile, IMO, was because we were able to take advanatage of teh reosrt lounge. Most of the rest of the trip - at Pop - we hardly saw the resort at all. WE are mostly in thepark people. I like Pop's food court and transportation. AKL's pool though is WAY better (ThoughI also like AKL's transport.) The pool at Pop is nothing special to me. AS you pointed out, the Epcot location is a big plus....but the price is abig deterrent to staying there the whole time.
Another hidden plus of one night concierge was the complete itinerary they printed up for us - covered our entire stay! That was kind of cool!
On your transfer day, you can have a somewhat relaxed breakfast, since you aren't rushing off to a park - but see below. You can also use this as a chance to do something offsite - like eating lunch.
Another plus, if one stay is offsite, is that it makes seeing theother Orlando really easy and mentally better. Once you are on WDW property,it is hard to leave. I somehow don't mind losing vacation time to hit a grocery store when I'm offsite, but onsite, I really try to maximize my park time. I want all my waking energy directed at having fun!
The disadvantages of a split stay. Once you've been to each resort, then there will be nothing new to see. I love seeing a WDW resort for the first time. If you've not seen either place before, then a single stay is better.
Second, you do lose half a day. You have to pack up the first room, unpack twice, check-in. That's half a day you can't be inthe parks having fun.
Third, you double your risk of losing something important along the way - like forgetting that all important ADR list. Though many Disney folks are really great about helping out.
Fourth, your room may not be available until after three - either room. So if the kids need an afternoon nap, you may be out of luck. Usually not aproblem for us, but it could be for some folks. Ther's also a good chance one or both rooms WILL be available before three. Disney will transfer your luggage, but if you leave something important in a bag by accidentt, it may be several hours until you can get to it. So while not overwhelming, there is a tiny bit of stress involved.
Now my tips section ofhte post:
Transfers are easier if you have acar. Then you can plunk everything in the car, check in to the new resort at your own pace. Just don't leave anything perishable ina car in florida. May will already be plenty warm.
To emphasize teh above - chocolate souvenieers left in luggage in the trunk of a car in Orlando
will melt! Those expensive little Mickeys you paid so much for will be brown mush! Who wants to drink milk that's been in the car for five hours?

Really you can only transfer non-perishable groceries, unless you maybe have a cooler, and I don't want to be bothered will all that.
Pack your luggage so that you have a daybag for the short stay. If it's on the front end, pakc a one night bag. If it's onthe tail end, pack so that you don't have to venture into the laundry suitcase. Your final packing (or first unpackign) will be much faster than if you spend a full week in one place gathering stuff.
Another time we did a split, we stayed in a condo the first part. WE bought all kinds of groceries for nine people. WE still had aton of food when we transferred. It was crazy. I should just realize now, I don't realy eat in room food whe Igo to FLorida. Maybe some folks do, but I don't. I like a dorm frdige so I can have coffe with milk, maybe orange juice....but there's no way I'm going to eat lunch in the room, or eat a brown-bag lunch while I'm in the park. Buy groceries very sparingly. The big disadvantage of
Walmart, IMO is they mostly sell onlylarge boxes of stuff. I can't eat a whole box of cereal in just a few days.
I could give you more, but that's the gist of it! I will say I have done it a number of times all for very good reasons, and it can be worthwhile. I love AKL, but usually can't afford to stay there the entire time, and I woudn't take advantage of the resort's amenities if I did. The one time I stayed there for four nights I felt slightly guilty, since I wasn't there all that much to appreciate it. That said, my next stay will be at CR. Wish me luck!