I find the roads in Cyrodiil a little bit more lonely then they should :S Are there any mods that make more people wander the roads between the city's. Maybe also that SOME of them stop once in a while to drink or sleep when they pass and inn or a city. Another cool thing would be travelling merchants carrying they're inventory in they're inventory so that you can pickpocket it, eventually stoping in citys and sell it to the merchants there. Not sure if it is possible though...

I'm not sure everything you're asking for is terribly viable, but a place to start would be Crowded Roads, and Crowded Roads Revamped. I'd reccommend at least looking at the latter, even with the annoying "See readme" description, before using one or the other.

you could try
http://www.tesnexus.com/downloads/file.php?id=4820 (crowded roads 3 flavors)
or
http://www.tesnexus.com/downloads/file.php?id=4387 (tamriel travellers)
or
http://www.tesnexus.com/downloads/file.php?id=3958 (10 travelers)
and there are a couple of others -but can't recall the names...
about merchants- I can only think of black market merchants (who are in towns) and shady sam- who is just outside the IC walls... you could search for them if interested

Both of the Crowded Roads mods have Merchant Suppliers that carry their inventory on them, if that's close enough...