It looks like a hold of that size could fit 15 units per 200cm length, or 60 units, with space for structural rails and deployment gear. For comparison, that's 7.5x the capacity of the Trident II SLBM which was designed to accommodate 8 W88s.
In terms of potential, one W88 detonated in an airburst would produce a fireball over 1.56 sq km, an air blast to 5psi overpressure over 91.9 sq km, and 3rd degree burns over 233 sq km.
The scale of the human tragedy involved in a first-strike deployment of 60 of these things is too gruesome to write down here, but you can play with it on NukeMap [1] if you're so inclined. Suffice it to say that no sane government on the planet will want Starship to land anywhere nearby unless we're living in a global utopia where this sort of thing is unthinkable.
A sky full of friendly traffic makes the hostile traffic more difficult to spot, after all.
Your passengers do multiple g's to altitude, then go weightless, then go back to taking g-forces on descent. That's the vomit part. Not a great customer experience.
Meanwhile, the Starship looks like an ICBM to every early warning radar on the planet. It's only during reentry that it stops looking like an ICBM, but most missile defense strategies call for intervention in the boost phase.
Let's suppose that they address those false positive detection issues. If you're a military planner, though, you're probably asking yourself how many MIRV warheads could fit inside a militarized Starship retrofitted for a preemptive strike?