Firstly, two points here:
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AO does not, in any way equate to GI, and by that I mean bounced/indirect lighting, soft shadowing, accurate shadow penumbras, area lights, translucent shadows, emissive surfaces, etc. - AO is just one element of that. AO + dynamic light can in no way reproduce the same quality of lighting that you get from lightmaps/pre-calculated GI lighting. Not currently anyway.
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32x32 works just fine for the tree - there is enough lighting information there to accurately reproduce the GI needed (which is very important to look i’m going for) and any inaccuracies in direct lighting and shadows are bridged via a stationary direct light which allows for the best of both worlds - baked lighting and dynamic shadows.
Going fully dynamic with lighting is fine and totally legitimate if you are operating in a fully dynamic world, for my circumstance it is unnecessary; my world is mostly static as is my lighting and I want to be able to take advantage of that. Less ms spent on dynamic lighting means more room for complexity in other areas.
Painting a simple shadow under a tree is one thing, but then you have to think about all of the other aforementioned qualities that you would have to compensate for and paint in manually also - this is where authoring things turns into a time sink, especially if your scenery is continuously changing throughout development.
I hope you don’t think i’m trying to shoot your suggestions down, they are genuinely interesting and im definitely going to be considering that route if I cannot resolve this issue, but I want to explain why it’s important for me to go down the route of having baked lighting. I really wish there was a decent, cheap realtime GI solution out of the box with Unreal but as of right now that just isn’t the case. 