In proper risk, you only deploy (I think) about 3 armies at a time, this is the only fair way to do it so the first player doesnt get too big an advantage.
The problem with this is that it could take weeks before a game even starts. For example, in a 6 player classic game you start with 21 armies and 7 countries, leaving 14 armies to deploy. At 3 per go it would take 5 turns each before you even roll a dice.
Imagine it for a 3 player game on World 2.1 - you would have made 25 turns before you even start round 1!

If each player took a full 24 hours to make each move you are looking at 75 days, or two and a half months before you play! This would not only get rid of deadbeats, but probably every player on the site as well.
Each player deploying all of their armies at once would be grossly unfair to the player going last, and is not a workable solution.