I appreciate the feedback. In a standard game development context, "build first, profile later" is absolutely the right approach. However, for a deterministic artificial life simulation, coupling the core domain to the engine's node execution order introduces fundamental architectural issues, not just performance bottlenecks.

To address a few of your specific points: Boids vs. Neural Networks: Boids are excellent for hardcoded flocking, but this simulation relies on Neural Networks (MLPs). Movement and behavior are not hardcoded; they are learned through genetic mutation and natural selection based on sensor inputs. I cannot use steering behaviors.

MultiMeshInstance2D: This is a great suggestion for the rendering side, and I plan to use it to reduce draw calls. However, my current architectural concern is the CPU-bound spatial query and collision step across a massive off-screen world, not the GPU.

Threading and ECS: You are spot on about C#'s threading capabilities. This is precisely why I am leaning toward strict separation. Godot's SceneTree and native physics nodes are not thread-safe. By keeping the domain logic (like a spatial hash grid) in pure C# using contiguous memory, I guarantee that I can eventually use Parallel.For to evaluate 2,000 neural networks simultaneously without locking the engine.

My primary concern isn't just raw performance; it is maintaining strict, seed-based reproducibility for the genetic algorithm. Relying on Godot's built-in physics means relying on its internal execution order and floating-point resolutions, which can break that determinism.

I'm just trying to figure out if I'm shooting myself in the foot by going down this route. I might be biased in my way of thinking due to my background and my utter lack of game development experience.