My personal opinion is that reducing slots doesnt fix the issue. It might guarantee that everyone has something to do for roundstart setup if we ignore apprentices (1 person on SM, 1 person on INDRA, 1 person doing stuff like RCON and sheilds), but the rest of their work is reacting, and how many people can reasonably be involved in a situation and have something to do is super variable on how severe the situation is, or how many different situations there are. If theres a broken window somewhere, thats still just one person that gets something to do. Lowering the slots down to three doesnt suddenly allow for more people to be involved with that situation. Ive also experienced during more chaotic rounds times where even a decently filled engi department is stretched thin.
Also, this hurts the liveliness of the department since lobby RP is like half the fun of the role and now youd have to deal with some intense slot competition.
Realistically the best way to solve the issue is a few things, I feel. Firstly, Engineering just needs more to do. I dont have any good ideas of this, but more things to do means more people get to do things. Secondly, and this is more of a culture thing, just stress that people should communicate about what theyre doing, when they finish it, etc. If theres more communication about that, then you can avoid the situation where you end up going to fix something just to learn it was already fixed, and it opens up opportunities to takeover a tasking if you had a chance to state your interest in something before someone else dealt with it. More dialogue and talking helps keeps everyone involved and active. Granted I do think people are generally fine at this already, for the most part.