I think this idea is good but there are a few problems that I can see. Firstly, assuming an in-game rank/icon will NOT be added, even if there is a forums rank added, when someone claims they have the respected rank in-game, some new players might immediately assume this is true, rather than going to the forums and searching to confirm that rank. Even if they did try to verify people's claims every time, it's a strange hassle to go through when people in the past and currently, simply ask in the friends chat if someone is BS'ing or not. What this boils down to is that an in-game rank would likely be required else I feel this addition would have minimal influence. Secondly, I don't see the point of these ranks gaining access to staff accounts for services, be it support or moderator accounts. There are a few concessions that staff members make when taking on their role, and among them is sharing their account details. I simply think this is too easy a way to gain access to a staff account, even if it's temporary. The possible negatives outweigh the potential positives for me. Additionally, it is very well known at this point if a staff member is online or not. Imagine the players who are asking for help only to be constantly ignored or constantly re-directed to another person who can help them with their ;;ticket or PM. We have many staff online at all times but I still see this as a possible issue.
As for your 3rd point, I don't really see any problem with it besides the before mentioned gripe with only having a forum rank.