I had a very interesting discussion over on Google+ today, based on some thoughts from Brendan from http://untimately.blogspot.ca put forth.
The initial discussion was about movement from this post: http://hackslashmaster.blogspot.ca/2012/09/on-movement.html
I thought I would have some interesting insights to share, because I've actually done a few things which are similar to dungeon-crawling. More similar than things most people have experienced, at least.
Sometimes, I gather a party, put on a suit of armor and a helmet, pick up a weapon and enter a dark, dangerous environment to search for treasure.
See, I'm a volunteer firefighter, which means that occasionally as part of training (not real so far, thank goodness) I do Search and Rescue practice. The dark, dangerous place is a burning building filled with smoke and the party is my rescue crew. The armor and helmet are my Bunker Gear, which is similar in weight to chain mail, and I carry a fire axe or a holligan tool. The treasure is a person, or at least a dummy which weighs as much as an unconscious person.
I also carry a flashlight and wear an SCBA. I usually look like this guy, although he's using a slightly different tool.
It's hot, confusing, exhausting and scary. The weight of the gear limits how fast you can move, and you often have to work by feel in a limited-visibility environment. If there were monsters in there, you probably wouldn't see them coming.
But then, if there was I chance I'd also find (and be able to keep) a huge bucket of gold, it might be worth it. Likewise pulling out a person would be very worth it - although they probably wouldn't let me keep the person either.
Of course, I've also held gold, when I worked up in the Yukon. An Good Delivery-sized gold bar can be as much as 30 lbs, needs to be held with both hands, and you sure as hell wouldn't want to drop it on your toe. It really makes you appreciate encumbrance rules when you do that - although I don't tend to be too sticky on encumbrance either.
But now I'm getting off-topic. In my own game, I tend to rely largely on quick judgement made on-the-fly for rulings. D&D Next's difficulty system seems to support that style well so far, but that style requires that you have a guy feeling for how hard things should be in order to set DC scores.
So let me tell you - crawling around in a dungeon, in armor, with all your gear... it's really hard. There's a reason that professional firefighters make fitness a major priority. Things like jumping, climbing and swimming are severely limited or nearly impossible, and fighting would be exhausting in short order.
Of course, it's a game, so do what's fun. Game on!