There could be a saddle bag designed to look like a folded tubular tire- that would look proper...
I don't like the look of a tool keg & especially a lump of stuff below the water bottle.
Water bottle cages are for water bottles.
For a clean aesthetic there should not be something that draws a double-take e.g. Is that a water bottle or something else?
All the cool kids in Socal just put their CO2 & credit card in their jersey pocket, don't they?