Normally I'm a big fan of vehicles in shooters, but in this case I would be incredibly insistent that vehicles should only be in the game if they fit with the quirky paint theme (rollers, paintball guns, etc.), and that they should otherwise be left out. I actually have an idea of how that could be achieved:
The vehicles could be at least loosely based on the trucks that paint stripes onto roads, like so:
I say "loosely based on" because obviously a vehicle in this game should cover more area at a time than this. For example, the paint sprayers could cover the full rear of the vehicle rather than just a single unit on one side. See the next image for something closer to an appropriate scale for a vehicle.
Conversely, the road marking-inspired vehicles could
remove all ink from the areas that it covers. This would add a strategic element that differs from the current game strategy in that it would be incredibly useful for areas that are filled with the opposing team's ink, causing them to lose turf (unlike simply painting over the spot, where it was said on a Treehouse segment that the ink is still present underneath and thus adding to the opposing team's turf advantage). The potential disadvantage may be that hitting the fire button to activate the paint remover can also remove your own team's turf if you're not careful with where you activate it. This depends on if friendly fire is possible in Splatoon.
I could imagine this working in one of two ways: either it removes just the top layer of ink of whatever it's moving over, or it removes all paint below it and leaves the clean pavement below. Furthermore, their inability to climb walls and lack of maneuverability could balance them against high durability and potential devastation to a team's turf advantage:
However, as I continue to think about it, large vehicles like these trucks might not fit with the game due to the wide open, uneventful spaces they require to maneuver. Nevertheless, they could be quite imposing to see, and would be highly durable to make up for their lack of maneuverability or speed.
Thus, this would likely be a more fitting option:
This model of paint remover is smaller, more maneuverable, and has an open driver area for fast entry and exit.
Of course, paint removers don't need to be vehicles at all if the concept is acceptable but vehicles would require too much of an overhaul to game mechanics. Here are two variants of semi-handheld paint removers: