^But when do you pick the number, at the end of your last post or after the posted action is complete? Some situations might not need dice too.
If I were using my walking system for PBEM, I'd tell the players to bracket the numbers they pick and put them next to the action they want to roll against. Like I said earlier "I pick his pocket ", and then the response was [18 / 3], so the number the GM picked was waaay off from what the player picked. By posting the player's number-slash-GM's number in brackets, the player sees why
the NPC detected the failed attempt and responded with violence.
If you don't think you need to roll, don't. If I think you do, I'll tell you so. If you think you need to roll, but I don't think so, I will ignore the roll and move on with story.
The major advantage of my walking system is that there's no need to trust the player's rolls, as it's compared to a random target, not a fixed target, so players can't cheat, and nobody has to use a third-party site for cheat-free rolling.