Both variants would be a fair bit of work. Assuming they are possible at all.
Teleporting to a location (in front of quest) would need work to build those markers and getting the teleportation system (NPC or Item) going by linking them up, doable, but you would need to spend time to build and add in the locations of each quest entrance by hand. And the benefits are questionable as not all quests are out in explorers but in hubs already. But then, if you don't do them all, is it really QOL? Also, teleporting to an entrance to a quest overlaps onto players just buying Bracelet of Friends and summoning them that way by players who get there first or showing newer players the location. A thing with all stuff like this, is if there's an overlap, there's an even less chance of it being made.
The other method, enter any quest, likely won't be doable because of how DDO is set up; you can port to a pre-set location, but as a quest is an instance of an area that's pre-made. But you can't make a teleporter to reach the inside of a quest as it doesn't exist yet. So your alternative option is to build something that lets you reach any quest from anywhere instead (a mobile portal that can select any quest to enter). But if you build something like that, you need to link every quest in existence in DDO, keep that updated for all future quests. And the UI for that quest selection is going to include everything available, so that's a lot of work to get done, and in the end, it might not beat a player who uses a Bracelet to bring the rest of the party over, or players just running over to the quest instead. It's basically the Tea Party quest in Ravenloft; why teleport out to it (by selecting it from every quest available that you'll need to scroll through), when it's just around the corner? But we go back to; if it's not included, is it really QOL?
J1NG