I tend to think of things much in the same way that you do. When evaluating the financials of points ownership, we never compare against booking on Home Away, Redweek, VRBO, AirBNB, etc. Too many hassles and risks dealing with other owners, as you allude to. I always compare ownership against the actual ways we would book if we didn't own - hotel online sites, Orbitz, Expedia, etc. or in some cases dealing with a Realtor who has a condo rental operation on behalf of owners. (There we are renting someone's condo, but are dealing with the Realtor, NOT the owner themselves.)
By contrast, many (most?) TUGgers are much more comfortable investing the time, energy, and risk of renting from an owner in order to save some money. So if you are looking for the best possible deal, comparing against a $2500 Redweek rental makes more sense than comparing against a $5,000 booking on Marriott.com. Also, many on TUG are legacy weeks owners who are not totally sold on buying MVC Trust points to get the flexibility and value of the Points system. These points
are more expensive than legacy resale weeks, but as you have figured out, Points come with advantages as well. I think you should pay attention to what everyone is saying, keep an open mind, and consider whether any of their very informed points apply to you - but always keep in mind that TUGgers are a group that is much more willing to play the timeshare "game" than it sounds like you are.
I do agree with Fasttr in post #19 that if you are financing the purchase because you can't afford to pay cash, then I would reconsider since MVC financing terms aren't usually great and I'm not a big fan of using debt for a discretionary luxury purchase. But if, on the other hand, you could pay cash and are just using the financing (and absorbing the financing costs) as a way to get the bonus points, then maybe financing is OK based on your numbers. Some have suggested looking at a Hybrid Bundle as the best way to get a better price point on Points ownership, and that is usually the case (that's what we did in 2014), but most of those wind up costing in the same $7-$8/point range where you are already at price-wise, so I'm not sure if it would be worth the "rescind and replace" strategy.
Many TUGgers recommend buying the minimum number of points (1,500) and then renting what you need each year on
www.vacationpointexchange.com (VPE), since those points can be "rented" (actually its a points transfer in MVC terminology) for about the same cost as what you would pay in maintenance fees on owned points. That way, you totally eliminate the up-front cost. That is a good alternate strategy since, while VPE rentals are another consumer-to-consumer transaction just like renting on Redweek or VRBO, the transaction is usually totally electronic with payment via PayPal, and once the owner has transferred the points to you, that owner is totally out of the picture and the points are yours to do with as you wish (unlike a condo rental from an owner where the owner is essentially acting as your landlord until your check-in/out). Rented (transferred) points, however, cannot be banked, borrowed, or transferred again, so they are stuck in the use year you acquire them in. As a result, you have to plan your points needs carefully, and a trip cancellation could leave you with points that can't be easily used. For that reason, I think points rentals are a better strategy for occasional years when you need more points than usual, rather than as a permanent alternative to owning points. There are however a number of TUGgers who use point rentals as their primary points strategy.
So I do think that you are approaching this decision to purchase in a methodical and financially consistent way - and have done a good job making an informed decision. Some may disagree with looking at the finances this way, but the way we looked at our purchase in 2014 was very similar to the approach you have taken to validate the economics.
In your post you mention the use of Points for cruises, tours, hotels, etc. I will caution you that your 4000 points won't go very far in the Explorer Collection. You may have to combine two or three years worth of points to book some of those items, and may find that booking direct for cash is just as cost effective. In most cases, MVC has to acquire that inventory from other companies, so it is not as cost effective as using points at an MVC location.
Another caution I will offer is to not assume that booking a Marriott timeshare is as easy as going on Marriott.com or orbitz.com and booking something. Timeshare tends to book much, much farther in advance than the hotel sites do. If you are wanting prime time in Maui, summer in Hilton Head, winter in Florida or the Caribbean, etc. you need to be prepared to be online and/or on the phone right at 9am on the 13-month or 12-month inventory release day. Even then, you may or may not be able to get exactly what you want. Timeshare inventory is limited, so people tend to move fast. So while there is still something of a "game" to any timeshare booking, I absolutely agree the MVC Points system is the closest thing I've found in the timeshare world to just going online and booking a hotel room or condo. It's much easier and less stressful than the old timeshare "weeks-based" trading game through II and RCI. Just don't expect it to be totally without "gamesmanship" or you may become disappointed. So far, we've always been able to get exactly what we want using the Points system, but others can report less successful experiences.