My favorite quest from Fallout 3 and possibly any game i have ever played is Tranquility Lane. No quest was more fun and interesting than the environment presented in Tranquility Lane.

Im not saying directly rehash the quest but i would love to see a cool simulation environment and that is really interesting to explore and is filled with its own cool little gags and trinkets.

No point redoing something that has already been done!

There already has been two variations on the simulated environment: The invasion of Alaska and Tranquility Lane. What you are suggest would just be going back at the same place to drink at.

The memory den could offer up something similar.... then again, all we can do is speculate what the memory dens purpose could actually be.

Maybe relive memories of your old life before October 23, 2077?

Kinda looks like there will be some form of http://vignette2.wikia.nocookie.net/fallout/images/4/42/Memory_Den.png/revision/latest?cb=20150608164537 dedicated to the http://vignette4.wikia.nocookie.net/fallout/images/7/71/Fo4-memory-den-concept2.png/revision/latest?cb=20150617102822.

Edit: Given that most people's memories would be pretty terrible, being post-war and all, I'd wager that they would be selling pre-recorded or pre-synthesized memories from before the war and not your own. Kinda wonder if the owner would pay to record your memories since they would be pre-war ones.

A simulator which recall memory is a good idea

Maybe your character decides that they want to experience being a spy for a day then the people putting in the experience realise that you were already a spy once?

Bethesda likes to repeat things that people had fun with before, so I can see something similar in F4. Just like they're, seemingly, doing with coping Moria's Survival Guide quest chain into F4 via (I believe it's Piper?!) that runs a local newspaper and wants our help. I see that quest chain as her wanting us to research the areas in the wasteland.