Would this preclude the powerful Southhampton, Gloucester, and Edinburgh Classes? Unlike the weak Treaty Cruisers those 12 gun ships could match any Axis cruisers afloat with the possible exception of the Deutschland Class when they were rerated as heavy cruisers.
A WNT limit of 7 - 7,500 tons would suit the RN much better than the OTL 10,000.
I think everybody building 10,000 ton 8" cruisers as the only type came as a nasty surprise, and the RN felt obliged to do the same.
Being able to build a larger number of cruisers to cover the worldwide needs of the RN, at a lower cost, would be good for them.
Everybody else's cruisers would be subject to the same limit, so no pressure to build bigger.
So no Raleigh or County cruisers (but also no Pensacola, Northampton, Furutaka, Myoko, Duquesne, Suffren, Trento, Zara).
Notable that after the OTL London Naval treaty France, Italy, and the UK all switched to smaller cruisers, while the US and Japan kept going with 10,000+ tonners.
As speculation, an ATL treaty analogous to the London Naval Treaty may well have allowed larger cruisers, as both Japan and the US wanted the bigger ships for Pacific use.
However GB could have extracted concessions for that, such as quotas or ratios (?e.g 2 10K 8" = 3 8K 6" = 6 5K 5"?).
After the OTL London Naval treaty UK went back to building some larger cruisers in a perceived need to compete with the US/Japan large cruisers.
After a hypothetical ALT LNT follow on treaty, who knows?