First for the new Fertilizer type. My suggestion is to be able to take a compressed plant ball and dirt and be able to craft it into a mulch that would act like a low-grade form of Fertilizer. This would have the benefit of not having to rely on skeleton bones or a recycler unit to produce, but would be much less efficient than fertilizer (and maybe bone meal, depending on how much that adds to the soil).
For the chainsaw I suggest another power mode that would fell the whole tree at the energy cost of what it you normally take to cut down all the blocks felled plus an extra percentage for using the mode (like 5-10%), if possible. I'm not sure IF the energy consumption based on how many blocks that come down is feasible as I'm not a coder myself, but I would like to see something like the Timber! mod implemented in a way that doesn't just make energy use a non-factor, especially since we're seeing trees that can easily consist of over 90+ blocks in the jungle biomes, and while being able to climb a tree to the top of the world and spend 5-10 minutes chopping it down might be fun the first two or three times, it can be repetitive.
As for the auto-fertilizers and hydrators you have in the works, I'm not sure how they'll be implemented, but I'd like to see something where you can have two blocks, one that uses the items it has to fertilize/hydrate crops, and another that you can connect to them via special pipes that would distribute the items to the other machines that use it. I know it sounds kinda like BC/RP2, but I'd like to see something more like a macerator or other machine, where you have an input slot, but the output slot is a different machine that's connected to it. I'm sorry if that doesn't make any sense, but I hope it does.
<-- Chop this to manually get the wood.