Right now /quirks is a hodgepodge of settings that we tend to think of as only mattering for test levels. A few old non-test levels (particularly BlurredD's Survivor pack) make use of the "get stuck in ceilings" part to test whether players are Spaz, but there are scripted solutions for that which are more reliable and are easier on the player. And because /quirks is something you turn on in response to specific things in the current level, it seems likely that when one person wants /quirks to be on, other players probably want it too.

Therefore, there is a strong temptation to

1. Make /quirks a server setting, rather than a client setting, along the same lines as /allowwalljump: all players in the server either do or don't have these weird physics differences available to them, depending on what the host (or remote admins) decide.
2. Specifically, this server setting would not be named /quirks anymore but would instead be a new "Test" gamemode that would, at minimum, also prevent players from colliding with one another. Currently the solution to this is to host in a CTF-based gamemode but disable all but one team, so all players are on the same team; however, this has the unfortunate side effect of disabling colored names. A dedicated Test gamemode would get around this problem.
3. Additionally, apply all those same physics changes to the eventual speedrun mode.

In summary, getting stuck in the ceiling as Spaz (and the other weird stuff) would be possible in a server hosting the Test gamemode, or in a local Speedrun game, but in no other contexts.

Are there reasons I'm not thinking of that this would be a bad idea? Let me know!