I struggle to see it. The advantages London had (long history of stability, Sterling as a major reserve currency, pragmatic and reliable legal system, agglomeration effect of existing firms, pipeline of workers with the right skills and, crucially, attitude) are gone and aren't coming back any time soon. There is more to being a financial centre than just wanting to be one, it requires hard policy choices that tend to have a negative impact on other parts of the economy. It's why Paris never made it, despite talking about it for ages successive French governments didn't want to pay the price in terms of domestic impact. It is not a cost free decision and I struggle to see any CW government actually following through.
I await this with due sense of dread and trepidation. Feels very much like the the light at the end of the tunnel being an oncoming train.
No. I've fallen into that trap myself at times and I think it better to look forward and work on new things. There are always old chapters and plot threads that current me would do differently or not at all, but in a few years time that will change again.
If you do wish to go back to those periods perhaps do it as a companion piece? The same period but from the perspective of other countries or the 'losing' side, that view can of course be completely different to what is portrayed in the main thread even to the level of disputing events and timelines.