Perhaps an enhanced Type 26 as a bridge between not having enough Type 26s and Type 45s would be a solution to keep yards viable until long term future requirements are determined or is there no chance for funding?
The thinking appears to be to get something small and relatively cheap that can be exported - hopefully with some being built in UK yards - the issue with Type 26 is that anything that large and complex, the purchasers want to build in their own yards. That keeps the ship design teams employed but does nothing to underwrite some of the costs of keeping yards alive ready for domestic orders.
Type 45 replacements may be hard on the heels of an end of build Type 26 however - they have so much orphan kit it's unreal (literally, I think they're the only users of WR-21 GT's, the Sylver silos will be unique to 45 as 26 is getting Mk41VLS (strike length I believe) plus the 4.5 inch gun and SAMPSON. There may be a really good case to retire them ..not quite early but certainly replacing them as soon as is viable may be a smarter move than working too much on mid life refits.
Even if the replacement pulled through SAMPSON to save costs, getting a hull that used MT30's etc might be a better bet than keeping them in service too long - I suspect they'll be viewed as an evolutionary dead-end and a very good example of how not to do risk management in a project.
Fantasy time - take the Type 26 hull and stretch it out a bit to something a bit bigger than Type 45, same machinery, keep as many elements common as possible, give the hull similar rafting and isolation as 26, focus it on AWD but include something that's definitely double hangar size, space for command staff or an embarked team for whatever purpose, pull SAMPSON and 8150 through into the new hull with the intention of replacing that a bit down the line, MK41 plus Sea Ceptor, that sounds like a viable way to get out of the hole that the Harbour Queen class seem to present.
I suspect they'll be one of the shorter lived classes in modern history as who the hell wants all the over heads of that unique drive train? I could be horribly wrong and they'll limp along for decades, sucking the budget out of the RN but I'd sooner see the back of them at twenty to twenty five years.
I'm told project Napier is running along okay with the intention to fit an additional diesel and maybe we'll see them deployed a bit more in future but keeping those WR21's ticking will be expensive.