Nearly all the things listed are possible here.
Doors and Switches - Done in scripts I have an item on the store that does this automatically. I'm surprised it hasn't sold better but many have probably missed it altogether.
https://www.tgcstore.net/product/26196
Quests - I've done this before as well. It's just a matter of knowing how to code. Pretty easy at it's basics but depends on the quest entirely. Two quests in this video, both are related and affect each other depending on the order taken. These two quests were quite complicated to get working and so to make a full RPG game you would need a more automated way of making quests. As you can see though, they are more complex than simply killing 5 boars or finding some gold.
Crafting / Trading - Done in my RPG scripts and others.
Sniper Enemies - Again, if you really wanted this you could fake it in code.
Climbing Ladders - Possible already with coding. This should be as standard though here, considering the Easy Game Maker ethos of GG.
Lean Left and Right - Pff, not really ever used that feature in games. Not a priority for me. As far as I know there's no real easy way to add this at present.
XP Levels - I did something ages ago before GG even existed, a farming script that covered this sort of thing. Many people have worked on similar things as well. Really easy one this overall. Once we get more access to player control and such the XP can even do something in the future to affect your players speed etc.
I can see some benefits from some of these features being included by default though as many people would not be able to code their own and even for us coders who can, some things would be much easier with an internal system in place. An inventory for instance would be far easier with a built in system already. It's quite possible to do your own, just means a lot more work overall. You would need to know you have picked an item up or dropped used/it. That means editing the default scripts to add that info into your own array or creating your own altogether. If that info was saved by GG already into a default array, you would only have to grab data out of the existing one, making things far easier to do.
Progress has been back at a decent speed again so far, let's hope it continues.
SPECS: Q6600 CPU. Nvidia 660GTX. 8 Gig Memory. Win 7.