I wouldn't mind it being a list of self imposed restrictions you can choose at character creation but it would probably be better if it was just one mode or a few tiers of one mode (normal, hardcore, etc)

Because I don't think modes like these have to be hard to be fun

In OSRS I play a permadeath (hardcore) Ironman and a regular Ironman, of course the hardcore one is much more tense but I intentionally play very safe so it's not hard, just time consuming, but I enjoy it

Regular Ironman, I take a little more risks and I've even died shortly into my run, I don't find it especially hard, I just find it satisfying because I can't immediately run to the grand exchange (marketboard)

I know I get all the dungeon handouts in 14 etc I'm okay with that, I realize just no trading no mb wouldn't be very compelling, but it would be just interesting enough for me to spend time crafting a bunch of my own crafters gear or actually getting a house and working for all my furniture instead of buying it, things like that

But I definitely condone like a no bank difficulty or no dungeon drops, etc other kinds of difficult to make it even more about self sustain with little help