I'm an architect and I have a few thoughts to offer to possibly help your thinking about your future dream home.

First up is I would strongly encourage you to keep all the pieces of the project separate in your thinking. In residential construction you're buying a printed drawing set and printed specification manual with architectural stamps on it - for commercial and high end construction, the product can be a BIM model but residential architects won't have experience delivering that product so it will take some research. The contractor is providing physical materials arranged into a house matching the plans and specs from the architect.

Just to give you an understanding of the precise basis of the current process, the dominant contract under which owner-architect relationships is governed is the B101 (https://content.aia.org/sites/default/files/2017-04/B101_201...) with some more sophisticated relationships described here https://www.aia.org/articles/210481-selecting-the-right-owne... . The legal standard for owner-contractor relationships is the A101 https://help.aiacontracts.org/public/wp-content/uploads/2020... The A101 and B101 together implicitly create the architect contractor relationship through drawings and specifications.

You can and should take as much control as you want over that process but just have it clear in your mind what the products are. The house you're going to live in will not be better or worse based on the means of creation but rather the product. Some methods will give you a better end result more efficiently, but many paths will lead to a wonderful, high quality home that you is exactly how you want.

What you will gain by controlling means of creation is the ability to control the drawings in the future if you want to make changes or repairs. BIM models are now delivered to clients in commercial projects because they offer great power for maintenance and energy use control in the future.

Relating to your interest in simulation and generative design: The easiest way to get into generative design right now is Rhino with Grasshopper. If you're primarily interested in energy simulation then adding in the DIVA plugin would help too. Grasshopper's built-in functions can handle the geometry simulation already. Grasshopper support Python as well, if you're fluent. Revit + Dynamo is relevant due to Revit's market dominance. Those are the standards to which FreeCAD's tools will be held, both in ease of use and power of output. Additionally, any unbiased rendering engine can simulate daylight for you.

I'm not aware of anyone using FreeCAD, but it's on my radar as something to look into over time. I currently professionally use Archicad, I have used Revit, and I have used Rhino and AutoCAD. Training on new software is very time consuming and switching for a single project would guarantee a loss for the architect if the traditional 10-12% of construction cost is used as the fee. If any of my firms had to use a new software and make money on a single project the cost would be about double.

I would suggest you aim at working with someone local to you since there are such wide differences between how things are done in different markets. Also try to get the contractor and architect on board early and together if you want the most control on the outcome. In commercial construction that's "design build" or "integrated project delivery", more or less. It will be hard to achieve that integration in residential construction but money talks and if you offer to pay the architect hourly and pay the contractor hourly for pre-construction services then you have a chance of achieving you dream process, but at a higher cost.

I wish more of the industry worked how you envision. I'm hoping to work toward that goal myself. Good luck when it eventually happens for you!