first, i agree with haze. it just destroys berries. second, generic sand teams? i think we should ban sand stream. hail is fine imo because i never see it viable, and it really deserves a time to shine. its also more berry friendly than not, as alolan sandslash can be MEAN with liechi. tspikes are also up for consideration. i really hate pex personally, and it has become unhealthy for the meta. every team and their dog has it, just to counter berries, which are really fun. also voolpool, i found how broken cinderace can be, and i totally agree it needs a ban. and incinerate too. i think theif is good, but not insane. but tapu lele and weavile becone insane. why does t lele even get thief? trick is ok in the sense that you just take away berries, because it isnt item removal. clef is a bit out of hand with it, however. also why is starf banned? WHY? also: i think we should do something like this: berries that heal status should fully restore hp as well. lum should set up safeguard. custap should give +10 priority to a move. i think that status heal berries getting a buff shuts down tspikes and mostly stall in general. plus, lum shedinja. i really like the idea of 3 berries per team, and... we should make a new berry that is basically rapid spin. also make a berry that is basically haze. i think that custom berries will make the meta seem more unique!
So I'll go through some of your ideas and add some of my own:
Sand Stream: Weather in general is OP but with Sand and Hail in this meta is great, you can ruin Endure mons instantly. But the issue I am having with the ones I come across is they are just not utilising berries. It's just normal sets that you'd usually see in a regular OU match. Is Sand Stream banworthy? I don't think so, but it's part of the issue in regards to an easy counter to berry strats.
Hail: Snow Warning is rarely used, but it can still be an issue. It's so rarely used because in reality, Sand outclasses Hail every time (besides Aurora Veil). Sand-Rush users are just more powerful, faster and better typings and the Sand setters follow the same kind of story.
Toxapex: T-Spikes are not banworthy imo, but once again, they are another popular counter for berry users, which is for me the main issue with the meta currently. Toxapex however is a little more of an issue to me. I don't think it needs a ban, but only if bans on Incinerate or Unnerve (or something) are implemented. Toxapex won't be as much of a problem at all if Haze was banned ... (just another ban example).
Incinerate: I actually thought that it was a great idea keeping this move in the meta, but in reality, it's yet ANOTHER great and easily accessible counter to berry strats. Another reason why few people are choosing to use berries in their teams. Banworthy? Potentially, but depends on other bans and edits.
Cinderace: In the current meta, as it's so similar to OU atm, Cinderace is having a great time! But I agree, it really should be banned. However, if there are further bans on counters to berries, theirs potential that Cinderace may not be as threatening / used (but I don't see a world where this mon isn't banworthy tbh).
Tapu Lele: If anything is OP with this mon, it's Psychic Surge - the ability to stop priority moves to help your Endure mons out. So I really don't want to see one of the only viable ways of ensuring your Endure mon will at least hit once (depending on weather) be removed from the game.
Clefable: Okay, so, Clef absolutely THRIVES in this meta almost as much as Magearna did. It has so many options for removing berries and ruining strats and is insanely difficult to predict imo. Unaware is just mean and it can be very difficult to take down. If any other bans are going to happen regarding counters to berry strats, then Clef will be the biggest problem afterwards and most likely will be banned too. But atm, as much as it is used and as versatile as it is, it's somewhat needed in the meta currently.
Berry Boosts: So as VoolPool said, adding knew berries to the game won't be happening, but I love the Custap idea! And I think if we wanna see the meta really shine, adding certain extra boosts to the other berries would be a great addition. Perhaps like you say, a Defog mechanic added to the activation of status berries could be interesting. Or for a Pecha Berry, it could heal poison status and remove toxic spikes from the field? Just throwing some ideas out...
Now hear me out:
What if the mechanic of the berry was at full HP only, you have an automatic Focus Sash effect if your mon is holding a berry and is hit by a move that will normally KO you? (for 25% HP berries)
No more Endure usage and it may make berries more appealing to use? Hazards will be an enormous counter strat, but there are effective ways of dealing with that. Sand and Hail will be a big deal too. Counters will still be an issue, but at least you don't have to predict with Endure anymore and waste a turn. I don't know, was just an idea :)
Making a new berry would be making this into a pet mod. Things that create completely custom things that are subjective are considered pet mods. This is an OM so we couldn't really do that. But I do agree with +10 priority custap. Starf is banned for good reason as it lets people get free plus 4 in stats and recycle for infinite boosts to where they have max stats.
So I understand why the Starf berry can be too overpowered, but in this current meta where you can barely activate a berry successfully let alone recycle it and keep those stat changes with the amount of counters going around, as well as forcing your mon to be below 25% health in order to get the effect anyway and having to use a turn to heal.... *breaths* the Starf berry doesn't seem to be banworthy to me.
However if more changes are added, the berry would become OP, so it should remain banned imo.