See This link for the NexusMods mod page, which has a description, screenshots, and a download of the built mod.
The mod has two parts:
- Collect Hay Without Silos: If you have no silos or they're full, the mod simulates the relevant hay drop code as if you did.
- Pull Hay out of Hoppers Anytime: The mod uses Harmony to patch the hopper interaction method to always try to pull at least one hay out.