For construction that will never happen. Do you know how fast people would get 99 prayer? I like your hunter mini game idea, but sadly the Old School team isn't big enough to implement mini-games to a large extent. This is why most likely we haven't seen Stealing Creation put into the game.
I would love to see more mini-games and skill related content. Bonfires, however, is a RuneScape 3 update which should stay there. Back in the real 2007, you had to light the logs by themselves and not an easy way such as a bonfire.
support construction additions, though i think a bank would make it just too easy. how about a trophy room where you can display quest items? an upgraded parlor that's more like an asian-style tea room?
like the hunter idea. maybe it could be linked to a hunter boss, where you have to track something all across rs (so with friends it goes faster) before finally finding the mini-boss hiding place which you can fight (or capture?) together?
like more craftable toys idea too, though i hope some would be useful in game, such as maybe craftable fishing lures that work better than standard bait.
again great idea having agility races.
i was against bonfires before but with wintertodt neutering fm anyway they make sense now. would also like log additives added to the bonfires update, so we can use bonfires that burn hotter to smith, and bonfires that burn cooler to cook with higher success rate. maybe the new items (powders or whatever) to be added to logs could be a crafting link update.