First let's talk about RuneScape gold the wilderness boundaries, before 07 there were no safe zone and this is the most fundamental of the current wilderness design, it includes safe zones. While you could claim that they should stay in place, they could disrupt ongoing PvP battles. They are advertised as a method of jumping into a safer zone. It is also a way to encourage fighting.
This means it is impossible to preserve the lawless area. Another issue is that current activities in the wilderness aren't allowed. What effect could this have on the wildlife?
Personally, I would prefer shifting the minigames (Clan Wars and FOG, securing Deamonhiem) and to other places. But, the three quests are where things get tricky. The Summer quest line and Defender of Varrock both contain large chunks of wilderness, but if that the quests will remain, I think that the best choice is instancing the entire quest. What exactly does that mean? It means that you'll be on your own once you have met the point of beginning your quest and entered the wilderness as part he defender varrack story. While this would slightly change the quest it wouldn't affect it in any way.
Green Dragons, armoured Zombies and Chaos Ele should all be kept the same. The best location to train is a bit dangerous. While the Corporeal Beast is interesting I believe it would be fun to have barrage runners go to the cave. However the boss mechanic for the Corporeal beast in RS is distinctive. Due to its high-risk nature you will have to be able to bank several times. If the entrance was relocated closer to the edge of the wildy it might prove more attractive since it's currently past level 20, the tele cut off point.
Summoning also presents a challenge and I'd much rather have to have a unique set of game rules, so while lending would be easily resolved by not allowing weapons to be lent in the wilderness, summoning combat level will need to buy RS gold change.