I'm sure ♦ mods can already do this, but it would be nice if us peons could pick migration targets like everyone with vote to close privileges can on most other SE sites. I've seen a couple questions get closed that I think would have made great questions on other sites.
This also necessitates selecting migration targets, since they're different for every site. Look for some suggestions below the fold.
We don't add migration paths until after the site graduates from public beta. Also, we don't add them just because a couple questions could have been migrated. We want to see evidence that questions are being flagged and moved by moderators significantly enough that it warrants a migration path being added.
Historically, Physics is your highest value non-Meta target for migrations, having taken 20 migrations across the lifetime of your site. Which, isn't a high number. And to that point, there has been a single migration to Physics in the past 90 days, and only 5 within the past 365 days.
Actually, of late migrations have gone every which direction. There isn't any one dominating site within recent migrations.
As Rebecca noted, we don't instate migration paths unless there is shown to be a significant demand for the need of the path, by high volumes of migrations. At this time, no target site qualifies.
