This is the only argument I actually buy. That said, it should be totally doable to make the /leaderboard bot integrate with peacock's
leaderboards. Peacock already allows downloading and playing contracts directly provided by f7sc on official epic and steam servers
through hitmaps' api.
It should be very easy to verify a major service outage by simply attempting to connect to the server with any other player's or admin's game copy; this is a non-issue IMO.
Unless there are actually in-game differences, there is no competitive advantage within a match to using peacock; the fact that console can't use peacock shouldn't matter as it's not as though this actually makes a difference in game. The only difference is that console players will still be forced to unlock items but requiring this for everyone because some subset of players are still forced to do it is just gatekeepey BS anyway, it says nothing about a player's skill in a match only about the amount of hours they've dedicated to playing the game in a certain way.
While it is true that it is theoretically possible for aspects of the game to behave differently, since there is no known example of this I find it hard to buy this as an argument, particularly since it is so accurate that it's accepted on the official speedrun leaderboards and scores match with known time calculation formulas in (tens of) thousands of cases.
There's a super simple solution to this: ban the use of unreleased items. This is not difficult to verify.
Easy: allowing peacock would not change the policy on any other mods being allowed as it's a completely separate discussion and allowing one should not affect the decision of allowing the other or not.