How about a simple conversion with the Milan Turret from the FV103 Spartan?
Good idea in general, but wrong period for mine: I want to do these as if they've just entered service in the mid 1960s when the British Army was on Vigilant and Swingfire. Milan didn't come along until later.
I'm still debating how to do a Swingfire vehicle, partly because I'm still debating how to do the section vehicle....
Section Vehicle Options:1. Use a standard M113 hull and just fit a Saracen turret in place of the commander's hatch.
2. Use an FSV hull, cut the entire FSV top plate out and fit a new one with an AIFV-style layout, that is, commander's hatch behind the driver, turret to the commander's right and a circular hatch (spare driver's hatch) at centre-rear with a 3/4 skate ring around it.
Swingfire Vehicle Options:1. Ferret Mk.5 style: scratchbuild a 1-man turret with 1 x MG and 4 x elevating Swingfire boxes (Using this turret on the Scorpion hull was the original scheme for the Striker). External reloading.
2. Striker style: elevating box of 5 x Swingfires on top of, or recessed into, the roof at the rear. External reloading.
3. FV438 style: raised superstructure with telescopic firing sight and 2 x independently elevating single Swingfire boxes. Under-armour reloading.
4. Original idea #A: if the section vehicle layout is standard M113, then fit 2 x single Swingfire boxes in the back ends of the sponsons. They'd elevate to fire, the blast would go out of the back, and they'd muzzle-reload from under armour in the lowered position. Fuel tanks would have to be relocated though, and they couldn't go in the customary external positions to either side of the ramp.
5. Original idea #B: if the section vehicle is AIFV style, delete the turret in favour of an MG on the commander's hatch, then fit 1 x twin Swingfire box (vertically stacked) inside the main hull line at the right rear. It elevates to fire (well away from the cupola, which is on the left) and reloads under armour like #A. The rear ramp is replaced by a fixed panel with exhaust ports to the right and the original side-hinged door to the right.