Sounds like a great idea. The part that I'm worried about the most is actually turning in the 4 diamonds at the end of the quest. Would be so painful to have to go back and kill every boss again if someone was camping the pyramid.
If you have smithing level high enough to make mithril bars, you can break even or make a tiny profit with superheat ore. Besides that stun alching is your best bet.
82 combat right now but I have 69 construction for the gilded altar (crystal axe + teak shelves). Just gotta get the 1.2m in mats before I can construct it :)