Make Avatars available under Biological Science. Also, make it (if possible) that avatars don't need to have a thruster suit with life support to breathe in space (assuming the avatars are robots)

This actually is probably implemented, I just saw the dependencies and saw SE was an optional dependency.

I think the main change for Space Ex was that the fusion reactor equipment was super high up the tech tree (it's not the base rtg).

I believe I looked into not needing life support at one point, but they were still working on changing stuff to support that

so maybe later when SE is actually stable?

Yes. I'll check the next time I'm working on this mod.

I'm using it on SE now, it's extremely useful and fun but I feel like it's definitely available too early for how late other competing technologies (ie. Spidertrons) are available. I feel like Avatars should be farther on in Biology than Spidertrons because they're more versatile (and represent something more advanced). My suggestion is that the research should take 2,000 science including Biology 3 Science, to set it after Spidertrons and add more much-needed active value to the Biology tree.

The head should require a Neural Supercomputer instead of Processing Units (or just Advanced Neural Gel, as the supercomputer also requires Energy 3). The Internals should require 2 Life Support Capsules and a Significant Biomass. Maybe also a Pump for flavor. The skin should include Vitalic Acid instead of water, and Experimental Bio-culture instead of (or in addition to) plastic. The complete avatar could require a Signal Receiver on top of all the body parts just for flavor (and the control center could require a transmitter instead of a satellite).

There could also be an Advanced Avatar alternate recipe made using a Life Support System 4, Naquium Tesseract, a bunch of Self-Sealing Gel and 50 life support capsules, that doesn't require life support in airless/plague atmospheres and has a few other perks like faster innate walking speed, higher health recovery, etc.
Just food for thought, but I think it would make this perfectly balanced to unlock it this way.

Space Exploration is constantly changing and I've never gotten super far into it. So, I don't particularly want to tie into it a crazy amount. I don't want to have to keep an eye on their changes to make sure the recipes don't drift

Hi, let me add another PoV.

I love SE+K2 and their style, production and logistic challenges. But I don't like too complicated game style with hard time & space restrictions (especially due to having limited time IRL), so, I like using utility mods, and making them hardcore feels weird for me, making them useless. Thus, I'd even prefer to have a setting allowing simplification, like 1 recipe for avatars instead of different recipes for separate details. And if you'll make requirement for later technologies, please add a setting to make this optional, to not make the game crazy for people who don't like it :)