T45 does have a facility to remove 'major components' of the engines through a vertical trunk between the engine rooms & the top of the funnel, that has bolted 'soft patches'.
However, I believe that the "remedial work" that's required, is such that they are effectively taking the whole GT out, along with the associated pipework systems. NO easy task the way the engines spaces are crammed to full !(If like me, you've had the privilege of being in one of the main engine spaces on any of the T45's you would understand that that is truly the case !)
In larger commercial ships, they might consider dry docking the vessel & cutting it into two to carry out the task. NOT something that the RN or any Naval Arc would consider with a modern warship.
Yes, I know that ships such as the stretch T22's had holes cut in the side of them to fleet in new / uprated systems into them in the 1980's, but the proposals & the R&D on how this is going to be dealt with are (I THINK) still at an early stage.
It might have been better if this 'issue' was actually 'leaked to the press', just as the ship entered dry dock for the work to commence, I.M.H.O.
SA
After carrying out FCDs on the Collins class, including major work on diesels (replacement of the crank), generators and main motor (rewinding) for over a decade, earning multiple engineering awards for their innovative "keyhole" surgery/engineering solutions, they finally started cutting the hull permitting major items to be craned straight out, intact, and worked on outside the hull.
With the Collins if you don't cut the hull anything you pull out has to be broken down to fit thought the MGR hatch aft, the conning tower (difficult to access as its in the fin), forward accommodation hatch and the torpedo loading hatch forward, plus the garbage ejector in the keel. Equipment worked on insitue often couldn't be accessed until other equipment was removed, meaning that equipment couldn't be worked on until refitted and adjacent equipment couldn't be accessed for any work either. No surprise submarine maintenance is so expensive.
Anyway, after years of pushing for the hulls to be opened up for FCDs, the Principle Naval Architect, supported by the new, engineering heavy, management team under Steve Ludlum and his successors, finally got their hull cut in the form of a "sun roof" over the Main Generator Room. This is a massive improvement but still not the ideal full cut where the entire 100 section where the main motor is housed would be cut off permitting the entire machinery raft top be withdrawn and potentially replaced by a new fully assembled, activated and tested raft prepared before the Boat even docked for FCD.
IMO there is a need to get away from designing to the minimum displacement possible and then keeping the resulting too small platform in service for 30 plus years and get back to larger for but not with platforms and limit their service life to 16-24 years. The RN is close to this than many other navies, introducing new platforms with proven systems (where possible) that are replaced at about mid life, these systems then find their way into the next generation platform.
The Type 45 was a new platform with new propulsion / power generation systems and combat system, probably too much to hope to do all at once without some issues arising. I am surprised there weren't more issues but believe had they built at least eight ships in two batches but preferable twelve in three, they could have mitigated many of the issues, restricting them to the first batch. Having extra hulls would have permitted them to take some extra time and remedy them thoroughly and efficiently.
