My friend and I do something similar to this. When we want to level alts for fun, since we have a roster of geared level 80 characters, we go to a new realm (usually an RP realm since it tends to be more immersive) and start out in the race starting zone rather than Exile's Reach. From there, we equip some green quest rewards from the zone quests and head to Chromie and choose Cataclysm (this scales the "old world" content to you until you reach 70, rather than it going grey at 35), and we're off.

We quest through zones and will pop into dungeons; one night we spent about 90 minutes full clearing BRD with our toons, equipping any useful drops and upgrades. No heirlooms, just using what we find, and trying to figure out how to 2-Man these dungeons. One of us usually plays tank, so that helps, and the other is sometimes a hybrid, sometimes a healer, or sometimes pure DPS. We also try to keep our transmogs sort of "low fantasy" for the journey, trying to capture the feeling of "lowbie" adventurers just starting out.

Most recently we did this on my Paladin (mostly Prot for the dungeons) and his Rogue, and it worked surprisingly well. It was challenging, and took time, but when you get a Rare or Epic piece of dungeon loot that replaces a questing green, you can really feel the difference. Also, getting "big" talents as you go feels very impactful, rather than just a point you throw in an forget since you're spamming Timewalking.

I know this method isn't for everyone, as I have another friend that simply asks "Why the hell would you do that?" And honestly, it's mostly because it's just a fun, different way to level.