I remember working with HTML DOM in javascript, if I loaded all elements at once the page would freeze until work is done. If I set a 1ms timeout between elements loading, it was enough to keep the page usable.
If this works there could be an option for map loading speed? I know is a long shot though, thanks for reading

(my computer is kinda old but runs games like Warframe, Fishing Planet, LoL, without fps drops)