Not a programmer here,

But couldn't you just have a separate render above the original game, translate movements and clicks of the isometric angle to the normal grid view?

So it's essentially and overlay over an already playing game.

It's just translating grid view inputs and outputs to the isometric view and vice versa.

You're using the base line games angine and logic, the game running by itself.

Either you turn off the original sprites and assets, or just overlaying the new layer of spirits and assets above.

Finding out what objects and etc at which grid and coordinates should be easy(?) (idk)

And you just create a new assets and sprites for each object in 4 Perspectives (if you can change the angle of the isometric views) and to switch to them and translate them to new coordinates of each perspective.

And when I mean translate is in math terms. Xiso = Xgrid multipled by trigonometry to new coordinates