For the bottom teams though it shoudl be easy, intuitive fun etc
I think the game should be intuitive and fun for all players. I agree that D1 should be harder than D4, but I am pretty sure most will agree that it already is.
I'm worried that your suggestions about making D1 "more expensive" and generally harder to win simply rewards teams that already have more money and makes it more difficult for newer teams. It already takes a long time to for new teams to make it to the top, we don't need to make it longer.
Also, this idea of making finals and B3 runs super unprofitable and making dynasties impossible may just bring us back to the old era, where teams would just essentially buy B3 championships by stockpiling money and purchasing unsustainable teams. The introduction of over-extension tax has made it harder for these teams, and thus easier for more sustainable teams to win. OE tax probably made it easier for dynasties to form (look at the current champion), but I'm sure most managers agree that it is a good thing.
To me the game as it is, already has a great balance between competitiveness and fun. Making D1 this super unprofitable place just seems like a step in the wrong direction. If the BBs want to help newer teams out, their plan of increasing the promotion bonuses is a great idea.