Ok let's take an example. If my calculations are correct, you will be able to get about 1500 mithril ore per hour at max (maybe a bit more, but with ~99 mining, high tier pick, etc. you'll be getting roughly this). At 200 gp an ore that's 300k gp/hour. Who the f**k is going to mine mithril for 300k gp/hour except 1. a new player who is training mining 2. a bot? There just aren't enough low-level/new players to do the low-level mining and smithing that right now is being done by pvm, so you're going to end up with an economy that depends on bots. Then again, we already have a lot of bots and people don't really care that much so maybe it's not a big deal.
I share this concern. What players have told us over and over for years is that they want skilling to work as originally envisioned. This is kind of a test case for that, an opportunity for skillers to put their money where their mouths are, as it were. If it doesn't work, we'll have to rethink how we approach this problem.