Tanking is difficult and people don't think to move out of the way, or run directly in-front, of a 65T vehicle that has very limited vision.
There are methods in place to prevent people from borrowing your vehicle. before you activate the vehicle get into your own group using the U menu. then activate the vehicle and you will have access to a lock/unlock command. Only you or anyone in your group can enter the vehicle.
In saying that, the server is a co-op server and requires co-operation, a fully crewed tank is far better than a single crewed tank, glad you are putting the hand out to try and get more players to utilise the heavy vehicles.
In regards to the restricting you from vehicles. to be restricted from vehicles you need a threat rating of 4, each person you damaged or killed, who reports your actions, increases your threat rating by 0.5 as default. For players on the watchlist, you are not, the threat increases by 1 for each report.
With that in mind to get to a threat rating of 4 you would of had to damage or kill 8 friendlies over the course of the session (6 hours).
There is also a dedicated Teamspeak channel for Ironside if you want to make use of it, server address is ts.straya.life. If you haven't been on the teamspeak before you will need to accept the improvement of security pop-up that comes when first joining.
or if discord is more of your thing you can use the voice channels in there at http://discord.straya.life/. Once you have selected the new session from "Voice Channel" you will need to go into "VC Commands" and type .voice unlock which will allow others to join you there.
If you have any questions, queries or doubtful points feel free to open a discord support ticket and select the I&A service. One of the staff will be able to assist you.