Let me take these one at a time.
1)
Unbalancing. The system is balanced so that characters have access to a certain amount of Karma per day, just like they have access to a certain number of recovery tests per day. It is supposed to be a limited resource, especially at lower levels; you are not supposed to spend it on every roll you possibly can.
Adventuring for half a day, doing a karma ritual, and then continuing to adventure effectively doubles the amount of karma you have available to spend. Encounters are easier when you have karma to spend than when you don't, but making things more challenging to compensate for mid-day karma rituals is a problem because you do not have two days' worth of recovery tests in the same space of time you're spending two days' worth of karma.
2)
Meta-gaming. The only reason this comes up as a problem is because of the episodic nature of the Westmarches adventuring style. If we were playing in a traditional campaign, we would have the time to make travel appropriately dramatic. Multiple sessions could be spent just travelling to an objective, because Barsaive is a wonderous and dangerous place. The restriction of getting to the objective, completing it, and returning in one session - four encounters, including social encounters - means that it is simply not possible to do this.
While mechanically, no Karma is spent during the travelling time glossed over, this does not reflect the the dangers of travel in Barsaive. Realistically, the characters should have reasons to spend Karma every day, which gives two equally realistic options: assume that they always do their Karma rituals first thing in the morning or last thing at night, which is why they start today with full Karma,
or have them start the day with less than full Karma to reflect what was spent the previous day.
3)
Not in keeping with Rules as Intended. Karma points, like recovery tests, are a per day resource. It is no more appropriate to spend two days' worth of karma in one day than it would be to regain all your recovery tests at noon and continue adventuring. If you want the resources of a new day, you should rest until the next day. If you are not able to rest until the next day for some reason, you should not be able to access the next day's resources.
4)
Really annoying. It is not my intention to make an
appeal to emotion here. All three GMs being really annoyed by this is not, of itself, a reason to do or not do anything. Nor is attempting to tease out the logic of
why we find it so annoying likely to be helpful, because it is an emotional response rather than a logical one. I note it because I want to be transparent about the fact that emotions are in play here. For me, the chain of thought goes: "Emotional Response ----> Analysis ----> Reasons!" rather than "Reasons ----> Emotional Response".
The only degree to which this should influence the debate at all is the recognition that GM burnout is a real thing. One of the ways we moderate burnout is by trying to maintain a sane pace (*coughcough*); another is by attempting to minimise the things that personally irritate us whenever it is viable to do so. For example, if the way poison works in this game bugs the crap out of a GM, they don't put venomous creatures in their adventures. This, however, is not one that GMs can choose to opt out of, except by deliberately pacing the adventure so that there is only one encounter a day... which is actually very hard to make work, story-wise.