This idea seems to be "impossible" with the current / comming update, where eacht slot has it's own set of items, this 6th and 7th slot are now contradicting this move.
Thanks for catching the upcoming change and its implications. Given those upcoming changes (trying to avoid spoilers here), maybe that mean the forum vote no longer represents forum sentiment, since the changes obviate/complicate some of the “pros” in the proposal?
Crafting queue: It seems to me that the crafting queue and demand would be unaffected by this change (demand might even increase while sleeping).
Additional slot: It seems that the 6th and 7th could still work the way slots do at the present moment--a kind of Jeopardy “potpourri” category, where it randomly selects any instant/building/item type. I'm wondering with @Enevhar Aldarion whether 7th slot might be overkill for most users (not for me personally).
Possible resolution: Letting 6th and 7th be completely random when some other slots weren’t could conceivably make them more appealing (particularly an added opportunity for petfood/military building). Alternatively, one could just drop the extra slot and instead increase the spell production speed, since changes might increase interest in catalyst converters. Or INNO could just add the crafting queue, and that’s it.
Or there just might not be demand for those feature(s) now in light of the changes.