I admit that's cool but, No.
Darkseid's presence must be in BvS in someway and not just shoehorned in setting up JL.
I prefer them to keep Darkseid for later...introduce the related elements first (New Gods and so forth).
Heck, perhaps down the line, they should do a New Gods movie
When Darkseid shows up, it should be Final Crisis like event. They did it bad with Origins*, Darkseid being JL's first threat (shouldn't be that easy to 'beat' Darkseid - conqueror of multiple universes, especially not with an inexperienced team of superheroes).
*Although Johns is making up for that, via Darkseid War.
JL threats:
I would love to see
CSA - maybe for JL2. This introduces the concept of other universes - and potentially sets up an Earth 2 movie down the line.
(If WB/DC ever wants to 'abandon' this universe...they can do so...introduce JSA and explore that universe).
Legion of Doom/Injustice League - although that requires quite a lot of setup. Introducing villains first (DC's introducing a lot of villains through SS).
Martian War (akin to Morrison's white martian storyline) - yes, it's an alien threat. But, it's quite different from anything we have seen in CBMs.
Atlantean War - Now, this...I just want to see it for the spectacle. Giant creatures of the sea - Topo, Kraken and so forth)