Change difficulty settings on existing savegame

Can you please add the option to change the difficulty settings in an existing savegame? It makes sense that you cannot change mineral deposit sizes anymore, but stuff like base health and farming yield (so the complete second difficulty page) would be nice to have the option to change. And if here are some players that dont like to change the difficulty after the start, maybe there can be an option implented to "forbid" changing options after the game started.
Thanks!