b. put a base fee multiplier on transactions using certain opcodes (penalise only junk)
I like this option more since at the very least it makes abuse very expensive while satisfying those who claim "censorship"! But through script size threshold not OP codes because if we place any kind of restrictions on OP codes we may end up hurting regular users who aren't injecting junk into the blockchain.
i already explained in many topics and this one about conditioning the opcodes(looking for certain details). so the "penalise only junk" was related to that, having conditions and fees and penalties for just a subgroup of transactions.. much like is done by making legacy * 4 but in a more detailed and enforced way
i was trying to keep it short (avoid "wall of text") as it appears some other people dont read more then a couple lines before they get on the defensive
I may have a simpler idea - adjust the weight unit calculation and place x10 multiplier on script sizes >10000 bytes.
10 kbyte is too big though. Even a big ass multi-sig script containing 15 public keys (15*33=495) and 15 signatures (15*72=1080) barely reaches 2 kb (2000 bytes) and nobody uses such a crazy script.