[Please understand that I am not using 'you' in direct reference to anyone in this thread, but in regard to any artist attending AA, including myself]
Personally I am struggling to understand what all of this fuss is about. While I agree that it is ideal to have more time between confirmation of space and the convention itself, delays do happen. Complaining about the delays continuously will not make registration come to us any faster, and Krys has been nothing but polite, patient, and communicative while responding to questions and comments that have been quite disrespectful. There's a level of entitlement in them that is really disappointing, and has given AA's (or rather, the artists who attend them) a bad name at other conventions.
A-kon is a fantastic example of a convention with late notification. According to friends who are tabling in their AA, they JUST got their confirmation last week, and the convention opens May 31st. Kumoricon is trying to give us as much time as possible and we should still have approximately 1 1/2 months to finish prep, secure a place to stay, and secure a way to get there. This is, admittedly, not much time if you are traveling long distance like my table partner and myself are, however if you are local, or driving, this should not be a problem.
Even unconfirmed, it is free to reserve your hotel/hostel or plan to stay with friends in their homes. Hotels will ask for your credit card, but will not charge you, and so long as the room is not cancelled the day before the convention, cancellation is free as well. While I have no way to know if I will be going this year, I do have my room booked, and now I am just waiting to book my bus ticket (which can be purchased as refundable as well, but is often more expensive to do in the long run).
A solution to not rushing the production of merchandise would be preparing before even applying for a convention. Most artists I know work year round to produce new merch. This not only keeps you prepared for last minute convention adventures (I was once informed by a friend that I was tabling with her the DAY before the convention. Let me tell you, that's cutting it close), but keeps your products fresh and your sales booming. It allows you to retire products that don't sell well while keeping fans and attendees that might see you at multiple conventions buying. Without this constant flow of work, eventually people run out of things to buy.
Being prepared ahead of time also allows for you to work with inevitable convention delays. While we wish they were all as reliable as the Japan Rail, it's just not the case. It is never a convention's fault that you cannot get your merchandise done in time.
As it is, Kumoricon is doing its best to be accommodating. If the convention date is too close for comfort, or you do not like how the convention is being run, then don't go. If your merchandise would have to be rushed and you might not have the quality you would be proud of, or the quantity you need to run your shop in time for September, then it might be wise to look for another convention farther off. Or plan for next year.