I agree that the telephone idea is a bit of a stretch and overall, the artist did a decent job of giving us something that at least looks plausible but all those "hatches" on the front are a pain in the backside. I'm inclined to think that they added them just so the front plate didn't look so bare!
I thought of night driving lights because while the FV499 image seems to have normal headlights (although the image does look as though they might be fitted with some sort of shroud), it doesn't have anything resembling the night driving/convoy lights/blackout lights typically found on many Western military vehicles.
The position of those two round shapes on the FV499 is a problem for that idea though, it doesn't make a lot of sense that they would be stacked vertically when the more sensible placement would be horizontally. But I can't think of anything else that they could remotely be. The only other thought I had had was that they could be covers for electrical/comms sockets but that strikes me as even less likely than the blackout lights idea!
The turret is a problem, even thought its base is quite wide, it narrows so much at the top and with that sloped front plate, the roof is going to be about 2/3rds or half the size of a more traditional turret.
So yes, very cramped for two people, close enough to whisper in each others ear! The other aspect of the image that makes me think the turret is meant to be two-place, is what appears to be a machinegun next to what is presumably a crew hatch ringed with periscopes.
Another idea about those pods on the side of the hull, they could be countermeasures systems for missile i.e. chaff launchers perhaps?
The more I look at them though, the more convinced I am that the artist saw similar looking pods on the hull of some RM SR.N6 (without knowing what they were) and thought it'd be a good idea to add them to the image. A lot of the image seems as though they looked at various military vehicles and drew all the things that "looked right". For example, the smoke grenade launchers on the turret are very Chieftain MBT or FV432 APC style even though the turret looks like it was lifted from the SPz 12-3.
Actually, looking at a bog standard FV432 from head-on with all the hatches closed, I'd be willing to argue that the artist was told to take it as a base starting idea and turn it into a hovercraft APC
Again, I'll say the artist drew something that looks military enough without going into the silly Mad Max styles of some of those 1980s pulp war/post-apoc stories but it just doesn't have enough to really look like a properly designed military vehicle. So I guess what I'm saying is that you've probably got plenty of room for artistic licence
P.S.
For anybody reading this that isn't familiar with them, night driving lights are more properly known as blackout lights (I've also heard them called convoy lights). Some modern versions are shown on the wiki page along with an explanation of what they are used for,
https://en.wikipedia.org/wiki/Blackout_light
There's a good example of the earlier "shrouded light" style on the following eBay link, this particular example was apparently from a Ford GPW jeep.
http://i.ebayimg.com/images/i/172324...-1/s-l1000.jpg