So if I understand correctly you currently have a load of DeWalt tools but few DWalt batteries that work satisfactorily, I assume given the stated age they are all NiCad (stem style batteries). It is probably safe to assume they have little resale value and you would be ill advised to invest anymore in batteries for that platform. So I'm going to consider them a write off at this point.
You appear to have invested $700 in Ridgid and now have 3 x drill/driver, 3 x cirular saw, reciprocating saw, grinder, sander and light, plus 3 x charger and 6 x batteries?
I personally have only one Ridgid tool so can't comment first hand on their quality, but I can say that many people see them as more than adequate for general DIY use. Unless you specifically have them under performing against your particular needs, I would see no point in getting rid of them all to go with another brand, so let's rule that out.
I'm assuming you do want to end up with one of each tool but avoid duplicates? The problem I see is that it might be hard to shift the drill/driver and circular tools as bare because many prospective buyers with Ridgid batteries are going to have those exact tools. You are also going to struggle to sell them with batteries if you don't include a charger. So at best you're going to be able to keep one battery from each of the two kits and still be able to sell them. Then of course you end up with a load of tools, 4 batteries and only one charger and that is not a great combination either.
Honestly you might be best to sell two complete kits, particularly if you can get your money back or even a profit if it was that great a deal, and then use the funds to buy batteries and another charger (Ridgid actually has a 6 or 8 bay wall mounted charger which is really neat).
One final thought, how long do the batteries last based on the way you work? Having fewer batteries than tools is fine if you use the tools less frequently. On the other hand if you are screwing decks down all day long you are going to probably need several batteries to use with a single driver. Your tool and battery selection should match your needs.