I would suggest Battlefield-like way - image signature - easy to create (as server admin), easy to code (as mta developer), easy to understand (as player).
Example from Battlefield:

I'm crazily eager for the next nightly! I know GTA core code is fuckin complicated and it isn't easy to write some lines of stable code injecting into the messy code of the world-best game series. I also know it's hard to do it besides other things (family, job, another hobbies etc.). But it is appr...

I think Welcome Message is really better than MOTD. Here are the reasons: Who will change the MOTD every day? Who will read the new MOTDs every day? I think most of servers will have also website with actual events and changelogs