(Ok, I know it says seasons, and although it is the main topic here, I'd like to emphasize on a few other things)
I was quite shocked to hear that seasons had been halted because of problems back when they were a planned feature, but even more so when I found out they had been completely abandoned. As this was over a year ago, things were different but now, I want to bring this up again. Seasons should not have been left aside just because of a silly little feature, textures may not change, but that does not mean seasons can't be implemented. Yes, the visuals may be somewhat important, but put that in contrast to the function and main features of seasons, the defining feature is precipitation, weather and overall fauna and flora growth. This idea comes from serene seasons, a 1.12 mod that successfully adds seasons to Minecraft, though it is a bit rough around the edges I'd say. The LOTR mod already has a date system included, which technically settles it. The only thing to do is to define a season for each month and give each season an increase/ decrease in precipitation, have it snow in winter and storm more in spring or autumn and have each crop grow only (or perhaps slower if not) during its fertile season. This would make gameplay a lot more realistic, and players would have to know how to correctly manage their resources as crops would not be available in winter... well except maybe rhubarb, which actually grows in late autumn and early winter. In addition to this animals could also have breeding seasons, in which populations naturally grow in number.
Now that that's out of the way, for some extra things. To follow nature's example and have natural equilibrium, animals (like wolves and bears) should hunt other passive animals (rabbits, sheep, deer) at a steady rate. Not as wolves hunt sheep to extinction, but rather an occurrence every now and then. Even hunters would be a nice addition. These would work similarly to how farmers do, but instead attacking certain animals defined by the meat-type placed into a slot in their inventory, a radius in which they would work and a max number of mobs there can be in that radius of the same type.
Also going hand in hand with this could be a season-based temperature system to have some biomes be affected more or less by seasons. In the shire, one might not be able to plant potatoes in winter, but in harad, this just might be possible since it is a tropical area. This goes for trees as well and I might even go as far as saying that warm area tropical trees will not give fruit, or even grow in cold areas. Same goes the other way around, fir, spruce and oak don't grow well in hot environments.
Finally, to finish off I propose to have hired units require food to work, fight or survive. Just a little something extra to complicate and give things a little more meaning. And as for grass colour, I can't speak for the whole community, but I believe people would agree that these features are a priority to have grass be green in spring and brown in winter.