a) I completely advocate using vBulletin, but since in your case, it's a freeroam server then go ahead with SMF

b) I actually do not like deathmatching with no restrictions, as this will be a total mess, so there should be a /dm command or something like it for places made for deathmatching only (with killstreak rewards and you can make certain weapons that cannot be gained unless you get the required level). I also like stunt maps and teleportations because in a freeroam server, normal maps are just boring. There should be a race also done every 15 minutes or something of that kind by doing /race for example.

c) That is about everyone's opinion, as each person view this issue from a different angle, but in a freeroam server, try to add as much EVERYTHING as you can because a freeroam server should contain everything possible to attract the player's attention. Hope I helped and anyway that's just my opinion. Cheers