Well, I suspect it's a lot more than slipping the missile in the VLS cell. I'm sure that the AEGIS radar & combat system needs a considerable face-lift to be capable of being anthing more than a 'shooter'.
As I understand it, the primary adaptation required is a software upgrade...which is broadly transferrable to the rest of the fleet. Hardware-wise, the major requirement is for the transition to the SM-3...with the exo-atmospheric kinetic warhead. Ideally we should have already gone with the FlightIIa version which was the ORIGINAL DESIGN...but Clinton (via Madeline Albright and Strobe Talbott) killed it, so that it wouldn't be an effective missile defense. Squandering scarce Navy R&D monies...he shrank the upper stage from the conformal 21 inch diameter down to 16 inches...slowing it down and shortening its range substantially. [Pretext: to stay within the ABM Treaty...now defunct.]
Bush however has never approved the fix of this sabotage. Even though it would be a relatively inexpensive program, with a lot of bang for the buck so to speak. Either he has traded it away for phoney political promises made by Putin and China's leaders, or he felt we could simply dither a decade on this. Needs a good kick in the pants...either way.