We just bought 200 BLT points with the intention of staying in a 2 BR every 2 years. I really think BLT will hold its value better than the resorts with a 2042 expiration date. At about $100 per point resale, I think BLT is a bargain compared to BCV which costs almost the same upfront for a contract with 18 years less use. BCV also has higher management fees. The BLT point cost is higher for 2 br's with Lakeview or Theme park view, but not much higher if you book 11 months out to get standard view.
BLT is definitely a bargain compared to GFV which is now $165 a point direct and Poly is expected to be about the same or higher. We really wanted Poly
DVC but could not justify the cost. Poly is not yet for sale but I think assuming the cost per point stays at $165 or close to it, it would have cost us $10k-$12k more to buy points direct. That is the equivalent of the cost of the hotel room for about 2 stays.
I think you said you prefer BCV, but if you could "make do" with staying at BLT or any other resort taking your chances at 7 months then if you have the cash, I would consider buying resale BLT points instead. BLT 2 BRs have 3 baths which is great for a big family, and with 3 young kids, you can't beat walking to the Magic Kingdom. I realize timeshares are not truly a real estate interest, but still for Disney DVC I think the mantra "location, location, location" is so true. I think if you did buy BLT it would hold its value much better than other DVC resorts since the cost of other monorail resorts will continue to rise. If so, you would certainly make out and in a best case scenario, you could wind up essentially paying just management fees if you sell your contract a few years from now. Of course that is a huge gamble to take if you do not have the cash now to buy a contract. If you do have the cash to buy enough points to go every 2-3 years, and you think it is more likely than not that you will hold onto the contract to break even even if the value dips, then I think you should go for it. BLT contracts seem to be pretty hot right now though (there used to be tons but they seem to be dwindling in inventory).
If you are set on buying BCV then I think it is a much more risky "investment" but could be worthwhile especially if you think there is a good chance you could hold onto the contract until 2042.
If you plan to stay at BCV in the next couple of years, be sure you are aware of the upcoming refurbishments. Also if you are staying there for the SAB pool I would see if it will be closed during the refurb. It might be worth paying a very low per point cost for a stripped BCV contract if you want to avoid the refurb and use your points 2-3 years from now.
One upside to DVC versus cash rooms is that you have the option to stay in a Grand Villa if you have the points. I do not believe there are Grand Villa rooms through Disney for cash. You can rent points for a Grand Villa, but I think the point another poster made about being able to control the reservation yourself is very important. You can be more flexible and can see the resort availability tool to know all your options.
Also, rental costs keep increasing and at most places there now is a $2 per point premium cost for renting from 7-11 months out. There is no such premium if you own points.
Finally, when you rent points even through a reputable company there's always a risk that something could go wrong (whether it is fraud, the owner not booking the reservation correctly, or whatever). If you own points you control the reservation and receive a booking confirmation.