Water bottles on a tandem

Until recently I thought water bottles were not the most important feature of bike design.
But now I have to find a place for two batteries (electric tandem) within a tandem frame.
That takes a lot of fiddling around with batteries and water bottles.

Water bottles for a tandem are not features in BikeCad.
And I can only import one photo.
I use the photo for the battery.

Will it be possible to add a water bottle on the rear seat tube, diagonal tube, and rear the top tube of a tandem?

Thank you.