People are using 100% hot metal in electric arc furnace these days. They are using 4-5 oxygen lances for this. Roof of EAF is changed in order to accommodate the slag splashing.
I think the separation process is necessary to achieve higher productivity and reduce the time required for one heat.
In addition, the carbon injection process is totally opposed to the idea of combining (LRF) furnace with different smelting furnaces, and The most important thing is to adjust the chemical composition according to the class to be produced.
You can review the development of EAF to see the importance of keeping secondary treatment in a separate furnace (LRF).