1. How are council members picked?
How long can they stay on the council?
As much as they want to, so as long as no toxic behaviour or signs of procrastination are shown from these people, if someone wants to give up their position as a council member they should have every right to, as well as making an annoucement on the forums/discord etc. and wait out until the end of the season to give up his place for someone else, who should replace its spot, i believe a voting should also determine the new replacement.
What are the requirements?
Obviously owning a lot of knowledge regarding anything pvp is a must, so if they consistently put out good results, that's a great start, however i dont believe rating scores should be the only measure to judge someone worthy of this position. If a player who has consistently put out amazing results but hasnt kept in touch with the community, isnt very active and never participated in discussions regarding pvp, in my eyes, is not a good option for the council, i would rather have someone who isnt as good as the example mentioned above but has a presence within the community and has participated and if possible influenced the meta in the past, this shows that they do have knowledge about the game even if they arent the best in at it and always achieve number 1 on the ladder, they should be more comfortable and equipped in discussing a competitive meta than people who just play on the ladder, this isnt to say that any mediocre player who just happened to talk a lot in previous discussion should have a right to become a member of course, only those who actually have shown results in the past or currently and bring good and articulated arguments to any discussion, in general i dont advocate anything along the lines of "top 10 or 25 form each server should candidate for the council" as it doesnt truly portray the person's skill and knowledge of the game, especially when you have some people making in with really bad win% (no offense).
Should they be able to participate in ranked PvP while being on the council?
Absolutely, this will make them more informed and qualified to discuss a meta, makes no sense if they are getting their information from other peoples prespectives and not theirs, there wouldnt really be a point in making a council if they are being absent on something they should be supervising.
How would the split between Silver and Gold members look like?
There shouldnt be a split at all, the resources in silver and gold are the same, the only diference is the amount of players, the meta should be the same for both servers, if something is broken in one server, its the same for the other, same thing goes for something not being broken. If a council has 5 members and they are all from silver or gold so be it, if they are more qualified for the place than the other server i dont see why they arent more deserving of getting that spot.
2. How are suspect tests decided?
How does the council decide what Pokemon to sent into a suspect testing phase?
The council should have a discussion regarding whatever they think is suspect test worthy or has been brought to their attention from their community (an actual legit argument, not someone crying because they cant beat stall of course). In that discussion, if the members of the council reach a conclusion and put out their opinions, there should be a supermajority that agrees something should be suspect tested for it to go through, exact percentage would probably differ depending on the amount of members there are in the council.
How would a suspect test look like (a special suspect ladder is out of question)?
I believe a regular season is pretty good to take place for the suspect, this meaning that a suspect should only happen in the beginning of each season or maybe delay the season if it seems more convenient for players.
Who gets to vote after the suspect test is over?
Those who achieve the reqs i guess, im not sure what being asked here, seems like a pretty obvious answer.
What are the requirements to vote?
Something like achieving between 75 or 80 win% with a game range of 40 to 60 or 80 games sounds good to me, its a bit arbitrary on judgding what reqs should someone have to vote on a suspect but i think the reqs ive mentioned should cover mostly people with enough qualification to know what they are doing, and if possible maybe have the possibility of resetting your rating and record, to give a better chance for anyone who might've not been able to do it in their first "run", tho thats a bit hopefull of me.
What would council members need from staff in particular to make it successful?
How much influence does staff have over the council?
I believe staff should report anything the council may not know that could be of use, community's opinion on the competitive environment, usage stats (if possible) all that sort of stuff, not sure how much info staff has on pvp so this might be a dumb answer.
When can staffs interfere in the decision making process?
Only when the members seem dubious or corrupt, which lets hope this will never happen, in case that is a thing, the staff should have the right to report the incident and ban the player or players responsible for this.