Arena Scramble without use_queue:
https://forums.alliedmods.net/showthread.php?p=2226185

This plugins fixes bug of players stuck in team menu:
https://git.csrd.science/nosoop/CSRD-JoinTeamFix

Anti-afk system so idle players are moved to spectator:
https://forums.alliedmods.net/showthread.php?p=708265

For weapon restrictions you would want this, it can replace a gun to default one:
https://github.com/sapphonie/tf2rue/
Just create a whitelist here https://whitelist.tf, put it in cfg/ and set mp_tournament_whitelist "cfg/custom_whitelist_xxxx.txt".
It is recommended to at least ban vaccinator as it almost impossible to take down a duo who uses it on Arena.

List of restricted weapon on EU
- Demoman: Sticky jumper, Base jumper
- Medic: Vaccinator
- Pyro: Dragon's Fury
- Soldier: Rocket jumper, Base jumper

Server.cfg:
mp_autoteambalance 1
mp_teams_unbalance_limit 1
mp_timelimit 15 // 15, 20, 25 recommended
mp_respawnwavetime 10.0
tf_arena_first_blood 0
tf_arena_use_queue 0
tf_arena_max_streak 3
mp_scrambleteams_auto 1
mp_scrambleteams_auto_windifference 2
mp_bonusroundtime 5

tf_use_fixed_weaponspreads 1
tf_weapon_criticals 0
tf_weapon_criticals_melee 0
tf_damage_disablespread 1
tf_ctf_bonus_time 0
tf_crit_bonus_time 0

sv_allow_votes 0

mp_mapcycle_empty_timeout_seconds 3600

mp_decals 0
tf_spec_xray 0
tf_gravetalk 0

The restrictions and cvar values are not universal for every server and should be applied by your choice.