Factorio 2.0 Setting Recipes of Fluid processing entities

[FunMaker]

I currently play a game with AngelBob and https://mods.factorio.com/mod/crafting_combinator. It's nice gameplay and i know, that many prefer building ratio perfect production lines, but i got used to building only one site of a processing entity, hooking up everything with some logic, so that alle Recipes of the processing entity are produced by a demand and supply logic. So i got hooked for the possibility to wire assemblers and set the desired recipe as seen in https://factorio.com/blog/post/fff-394.
I was curious if setting the recipe will be possible for entities that process fluids like chemical plants.

The main problem would be to let pipes transport multiple fluids (not at once but depending on the recipe in the chemical plant). Wube decided some time ago to prevent fluid mixing, what i think was at the bottom a good decision but some builds broke as a result to the prevention of fluid mixing and chemical plants with changing recipes will collide with this. We know that some fluid mixing is still possible in 1.1: Placing blueprints or ghosts with a fluid producing entity next to a pipe with another fluid was not prevented and mixing was still possible. The fluid-mixing-prevention is in fact not handled at the pipe-transport level but at the building-entities level, so something like fluid-switching is still possible.

In my recent playthrough i got used to barrelling all fluids. This way i could put barreling pumps (or assemblers with barelling recipes) next to the consuming entity without any connecting pipe. This way setting the recipe of the barelling pump and consuming entity did not result in left over fluids in pipes and changing fluid-recipes was possible. So it game wise not a mixing of fluids in pipes...
But the restriction to put barelling pumps next to the consumer was very annoying because every chemical plant needed it's own barelling pump. So i would like to have a better solution.

The first thing that comes to my mind is a cleaning entity, that could be placed next to a pipe and with a pulse signal it could clean up the whole connected pipe to let a new fluid flow. Even the cleaning feature was put in the game some time ago - but not as an entity - just for the player to clean up pipes.

My question is, how this problem will be handled in 2.0? Hopefully this will not be handled with "not wiring chemical plants"...I am interested what comes to your minds. Maybe we will see some FFF about this topic...

Additional Question: How are left over fluids in entities that switch recipes handles? I think they will just be gone, i would be fine with that.