there's another rub to this, colocating (and maintaining) military capability in populated areas in times of war is one of those ugly things that triggers the various UN Conventions, Hague, Geneva, Berne etc...
I would imagine that the local population would get a tad excited at the prospect of turning into potential collateral targets if an enemy were unable to "guarantee" precision and containment of effect.
It certainly becomes an issue for all when you consider that military facilities built decades ago and usually in "isolated areas" have seen the civilian population progressively encroach upon or get closer and closer as population expands
Well, in the UK, basically, the concept of separation of military and civilian is a bit of a fudge if you start talking in terms of a nuclear exchange. I live 30 miles out from the edge of London and we're inside the "skin burns, structural damage to light buildings" template for a 1mt weapon. RAF Northwood (home to a tri service base and KEYCHAIN) is about ten miles or so south of me, nearer London. In fact, a large chunk of the M1 (the biggest North/South road link) would be danger close for a 2,000lb conventional LGB aimed at Northwood.
(I was helping out at a gig in Northwood one night and this grizzled submariner gleefully pointed out past the dance floor and explained that the bunker for KEYCHAIN was barely a hundred meters in that direction. Was very tempted to reply in a fake Russian accent asking for a slightly more precise bearing, while holding my mobile phone open to the GPS/Fix app but I figured there were too many Royal Marines present to bear that joke..)
You see some similar things even in the US, which is pretty big, where missile silos for Minutemen have gone from "out in the boonies" to "in the 'burbs.." over thirty years.
Coming back on topic, we're really stuck with the fact that CASD using four boats, with the active patrol boat out at sea is the most economical and minimum nuclear deterrent. It's out of sight, doesn't need anyone's permission to go places or break any laws regarding over flight (which switching to cruise missiles would!)
It's either give up the deterrent or keep it - there's no scope to reduce it's nature by much. I'd argue we could get more conventional use out of it using the new CMC if we bought a fifth boat, with the intention of using one for nuclear and one for conventional strike at all times, keeping three out for work up/training/deep maintenance.
You'd keep separation of roles, and see some sort of tangible benefit in terms of getting more cruise missiles to sea for conventional strike - I believe the CMC will have some arrangement to drop in some sort of sleeve inside a Trident tube to hold a VLS arrangement for multiple missiles making it fairly straight forward to change roles.