I ask the question as I’m not really clear on the role a FSV plays. Not really tank not really IFV. Neither fish nor fowl….If it was a cheaper (which is questionable ) and lighter but less protected option than a tank is there a place for it?
Everyone has already raised most of the good points.
The theory is that it provides a big bang for lighter forces where you can't take a tank. But, like all theory, it tends to break down. The biggest problem lies in being neither fish nor fowl. It's like the tortured offspring of an IFV and a tank.
Except it can't do either.
What you have in this particular case is a light weight 120 mm (so it can't shoot the same ammo as an M1). This to use against targets that have been designed against the M256-family of cannons to the point the West is considering going to 130 mm or 140 mm. So it can't shoot as well as a tank. But the 120 mm fires slower and has a greater danger area than the 30 mm / 40 mm / 50 mm family of cannon on an IFV. And those can kill anything short of a MBT just fine. Add in some ATGM to kill the MBT, and an IFV becomes a bit nasty.
Protection wise, this thing is huge. It claims to be 30 t less than an M1, but physically its bigger. So it's an easier target. Furthermore, most of that 30 t difference is armour. So less 30 t less armour over a physically greater volume? This thing can't take the hit an M1 can. And it's bigger, so harder to hide. All for a weight that can't be lifted on a C-130 or similar, so needs a C-17 or sea lift. Which is the same for an M1.... So deployability wise, especially for us, it comes with the same bill.
Finally, the sticker price for this is more than an M1. And that's before Rheinmetall add all their extras on. So you can get 4x M1 for the price of 3x of these.
So all up, it doesn't make sense, especially as their isn't a mission for it. Now, our FSV was to provide firepower for an air-dropped force. We don't need that now, because we've twigged that air-dropping forces is silly, armour especially. Furthermore, our airlift fleet has improved immeasurably since 1965, so if for some reason I need to put tank-like thing somewhere by air, I can put a tank. Even if you ignore that, I can put an armoured BG into the field in 2028 that will have a full power 120 mm, 30/35/40 mm, ATGM and 155 mm (plus maybe 120 mm mortar) shooting. Every vehicle in the assault will be armoured at least as much as a light tank, about 1/3 to half more so. And it will all cost less.
As an aside, the vast majority of light tank proposals have remained exactly that, proposals. There have been very few translated to production. It really seems a solution looking for a problem.