A mobile green house of sort. I guess allowing dirt on vehicles as tiles would be the way to go.[/quote]
dirt tiles on vehicle would be a little crazy cause can you imagine how big your vehicle would have to be to have any amount of meaningful harvest? on the other hand, a hydroponic rack thing would fit better because you get higher yield for less area usage. Which also holds true IRL cause the plants receive 24/7 light, nutrients, and water, not to mention you can stack multiple layers of plants growing practically on top of each other.
With regards to the source code edit, perhaps a halfway implementation could be just to make a new vehicle part(tool which use electricity), which uses a new recipe (seeds+water+fertilizer) and returns seeds and harvest after some time. Could be that this recipe gives you something called āplanted hydroponic trayā, which you place back in said vehicle part and then you activate it after some time to get harvest(kindof like the yeast culture thing)