Q: "Once you know the theme for a theme week, how do you decide which writers will tackle that theme?"
--Stephen, British Columbia, Canada
A: From Scott Johns, magicthegathering.com Content Manager:
Stephen, there are actually several factors that go into this decision. Once I know what an upcoming theme week will be, the first step is to make sure that we've got at least one column on theme each of the five work days. Fortunately, the fact that we do theme weeks and card previews is one of the key factors in how the columns themselves were scheduled out across the week, so this isn't usually too tough.
Depending on how deep the theme is, I'll usually aim for somewhere around 5-7 theme articles per theme week. The question here is how many different ways the theme can be approached before it starts to feel to redundant or too boring. For some very versatile or open-ended themes we'll even run them in every slot, like we did with Top 10 Week.
After that, the question is which writers are best suited to the topic. For this, it's a question of highlighting each writer's strengths while (normally) also staying within the scope of that writer's column. To use a specific example, Mike Flores is an outstanding writer when it comes to decks from Magic's past, so when the opportunity comes to feature that strength I typically jump at it.
Lastly, I also try to balance out which columns have been on theme when possible. Some columns are more narrow than others, which means they just get less themes. (Scott Wills' column is an easy example.) Because of that, one of the first things I look at with themes is giving the less-represented columns a shot at them when possible.