Royalist, a 1* friend of mine suggested something similar about 10-12 years ago, and I expect he wasnt the first. The suggestion was that instead of building ships in batches and then taking a construction break, whilst also refitting ships already in service at the mid life point, we sold ships off at about the 12 year point and replaced with new builds from the continuous pipeline.
This was supposed to give continuity of construction, preserve strategic industries and skills and also help keep other nations on side by supplying them with UK kit and expertise.
The problem is that Politicians only think in the short term and there probably isnt enough friendly nations to buy an equally continuous stream of second hand Type 23s or even MCMVs etc.