Treaty-exempt battlecruisers as rolling design experiments

What would battlecruisers become if naval treaties allowed unlimited construction up to 50,000 tons?

Britain would likely build them continuously as test beds, then use the latest successful battlecruiser layout as the basis for new battleships with added armour.

The Royal Navy would probably build at least one battlecruiser a year if treaties imposed only a displacement ceiling and no numerical restriction. Each ship could test a new layout, machinery choice or other capital-ship idea without waiting for the next battleship programme. By the time the King George V class appeared, its design would inherit the latest battlecruiser arrangement with heavier protection added. Treaty categories would therefore shape the tempo of technical experimentation.