Hardware --- why this PC/software minded approach just won't work with phones.

Phone hardware is all unique and proprietary and cheap (relatively speaking) --- due to manufacturing expertise and economies of scale. And the manufacturers like it this way.

Without this production/scale advantage, any "open" phone will cost 3-4x more for comparable performance. In other words --- it is destined to be a very niche market product.

The only hope for a mass market is to find a volume manufacturer willing to play along. Good luck with that.