b. not have the cludge of 1mb base 3mb witness. and just have full open access 4mb for transactions to fully utilise
This reeks of potential technical debt. It's something you've proposed on numerous occasions for the last few years now, but have never fleshed out. How, exactly, do you propose enacting this? Don't just give us the wishlist, tell us step by step what this option actually entails.
Something flexible would be great, like, block size adapts to number of transactions, i.e. one block gets mined every 10 minutes and includes 5% of all transactions. If number of transactions increase, block takes more transactions and block size increases and if number of transactions decrease, so does the block size. But that's probably not possible.
I'd also rather see something adaptive and dynamic. In the past I've advocated for such an approach. It likely is possible, but the primary challenge is that it has to stand up to game theory. If there are ways to manipulate or rig the system to an outcome which suits an attackers goals, then it's no good. We can't inadvertently introduce that kind of weakness.