I have indeed thought it through. I have dealt with machine learning models for 30 years, and I've seen multiple generations of recycled broken ideas, and I'm seeing them recycled now.
However, open source is not about giving out a model for cheap/free to whoever asks. It is about giving away the foundations that allow complete duplication, so that other members of humanity, smarter or more informed, can contribute and/or branch away from the work.
The cost of training is irrelevant. It merely reflects the low quality of the processes and ideas that are being used by the companies that currently build them. It's by sharing the raw materials and allowing others to solve the same problems better that efficiency and progress is made.
The current paradigms of pretraining, fine tuning, transfer learning, etc lead to an enforced conceptual modularity that is just a way to embed a middle man economy into the science: Some provider takes care of data for others, builds a foundation model for others, and they can tinker on top of that. It is counter productive and scientifically a dead end, while giving you the feeling of progress that comes from taking psychological ownership of the full system when all you've done is tinkered at the edge by specializing an existing model.
You don't get anything new that way, only epsilon variations on an existing body of work. It's a dead end, because successful intelligences in the real world all around us do not need anywhere near the resources expended on AI and intelligent biological systems do not function anywhere near the way these AI systems do. For example, nobody reads the whole internet just to be able to talk about a topic, and no animal brain works like a deep network.
If you want (scientific) progress, you must break out of the tinkerer mindset. Take the full set of preferred elements that build the full state of the art system, and be prepared to do radical surgery at any level that makes sense, because the current architectures are simply bad. You can't do that with existing "open" systems that lock you into these architectural paradigms and choices.
Your example of Olmo talks about openness, but I had a look at their website and I don't see a link to raw data archives. There's instructions how to train a model, and they discuss a token data collection called Dolma 3. But tokens are not raw data, most of the implied information is already lost once you've tokenized. They do a good job of describing in detail their process for dataset curation on their GitHub page though, which deserves credit. It's worth reading, because it shows how their models are being locked into patterns that limit them from the get go, long before the first weight is even being trained.