With all due respect, I'm not sure Merlin would want to give Spinball a new lease of life in another area of the park as it is no secret over the years that it is the most likely coaster to get the axe due to its low capacity and how its placement in that area of the park makes it stick out like a sore thumb. Don't get me wrong, it is a fun ride its just not suitable for a park of Towers' size when it would have been better of at a park like Lightwater Valley and if we knew that the ride to take on Spinball's place was a something like a Mack Spinning coaster which no doubt would work far better and if that were the ride to come in then I doubt many of us would really be sad to see Spinball go.
And regarding putting a coaster in TWODW which I'm suspecting you mean Coaster Corner? There is the problem of that area of the park in which has noise issues for the locals and I have said this many, many times that the only way to have a coaster built in that area of the park is an indoor coaster which would solve the noise issue though it would be a tight footprint.
Now regarding the topic of an S&S Free spin coaster, funnily enough I have been thinking about this for some time and while I can't see one coming to Towers, I have though suspected that you'd likely see one arrive at BPB and not just for the Arrow connection but rather that it would be the only sort of coaster they could fit on the park (I suspect that area where Trauma Towers and Wild Mouse were which I suspect they have plans for that area one way of the other) but it might give them a unique first for the UK that might work out for them, can't go worse than the disappointment of Icon!
Finally, one more hot take and that is I feel that if we are to get another SW project that this would be the last SW project we'd see at Towers for as it is already being said, it is harder to find a World First element for a coaster and I suspect Merlin are aware of this too, yes there is the S&S Axis Coaster which while looks really cool I'm wondering if one park has already gotten the first one planned to be built and even if Towers were to build it, where would they? Not down Thirteen? Not that I would mind TBH...
I'm still thinking that a UK first water coaster might be what we're getting but I'll likely be wrong with that and all my predictions above!