/t - Training announc - leaders could use this to give training info to legion members
No problem here
/s - Schedule announc - This is so we can post base attacks or base scanning schedules
No problem here. In fact, this would be very helpful
/r - Rules announc - This could be a box on the legion news page that standard rules could be posted for all to see
For this, I can see two categories. 1. The way you said, to explain the legion rules, for those who cannot join facebook pages, but this should be somewhere on the legion page.
2. All over every page, at the top, to alert legions members of rules that have been breached lately by a lot of members, or to remind them of alert policies

/c - Combat announc - This could be used to tell people to cease on alerted ships etc.
Yes yes yes. This could be very useful
I think those added to the current legion announcement would make communication legionwide much more effective.