What about doing abliteration, weight pruning, representation engineering, etc, directly to open LLMs instead?

Building an LLM from scratch has a hard split between a tutorial project you can complete in a weekend (that's useless for actual usage) and then a solid 1km high brick wall if you want to create anything actually useful from scratch.

Modified open models have a very active community around them, without the need to look much further than Hugging Face.