So, here is my vision about how should arena works.
Asuming a total reset with all people starting with 0 points.
1)Tiers: 10 divisions, Top3 this way:
T1 (5000+ points) = Top 200 players
T2 (4600 to 4999 points) = 201 to 500
T3 (3500 to 4599 points) = 501 to 1000
T4 to T10 (points to decide, with or without subdivisions) = depends on amount of players.
2) For make this dynamic and competitive, there must be an inactive penalty sistem. After 24hours of inactivity in arena, u will be marked as "inactive" u will start losing point dialy, more the high u are and more each day long (1st day -10, 2dn -15, 3rd -30 or something balanced). The higher u are, higher will be the points taken. Simultaniusly u wont be counted in the ranks so your place will be taken by an active player. Besides, you wont be listed in other players list so your defensive team wont be considered. This prevent your defense team appair in low elo matchmakings if u were in T2 and for inactivity u are now in T7 (for example).
3)Matchmaking... the hard one... This is complicated indeed, but there are some key about this.
Theoricaly, there will be people in each Tier, according their winrate, and points earned. We must supose that in low tiers is people with a low winrate or a few matches (because u need win points to scale here). Eventually will appair inactives from higer elo, wich ones descend and are now active again, big teams for a low elo. The solution here is a really simple filter. If i enter to arena and refresh my matchmaking list, the system must take 10 random players according to: Same Tier > Same Points > Same Activity > Same WinRate.
Same Activity is a good one because the more i play arena, the matchmaking will be more challenger, because ill have encounters with people in my same status, an interesting bath of blood the last day of the week... this is PVP about.
This must be totally independent from account status or power. Even arena team power isnt a realstic parameter to take.
4)Points earned. Here is no problem at all. According the matchmaking, the system will try to make challengers (but not imposibles) winable encounters. So to prevent farming medals team (people that put weak defensive teams to descend to farm medals in lower elo) we must to apply this: You will recive significantly more points and less medals if u are under your elo, this way you will scale fast to your real Tier wasting coins for nothing. The same apply for inactive people than join arena again, they will have an easy way top again, but almost no rewards in the process.
5) Defensive teams. As i said, weak defensive teams for allow farming will be a bad idea for players so encounters will be always a challenge. Even here we can put some Tier reward for "invictus" or "hardest" defensive team of the week, another incentive for players to make defensive teams harder to beat.
Here we can add to an option that allow a player to give the hit back to the attacker (with some restriction preventing the loop here of course). Arguable option, but can be fun, "hey u... give me my points back".
This is just an idea about how make arena more attractive, competitive and funny for all. No matters if has a lvl 1 account or 10 millon points. Just the correct champions with the correct stats will make the same difference for a F2P than for a P2W, at least in the middle/low Tiers.
GH and Ariber Arena´s missions should be reworked of course, according this new arena system.