That idle time can be reduced in minis...not only as countermeasure against intended afk, but also against people crashing or falling into the ground (like 4 mins instead of 15 mins, longer than it takes for fetching a drink, collecting a package from postman, answering a quick phone call or going on bio, but short enough to be relevant compared to total mini game time).
One solo measure might not be enough though, since it is easy for one in hide to just press a key and move a step, not changing the situation.
But...for example they could take damage dealt, damage taken or healing done etc. into account. In addition they can define zones, in which such an autokick from hide or idleness happens. If they move out and sneak around in hiding either to ambush or to avoid being zerged at the end stages, such behaviour is completely legit. So linking a kick purely on time in hide will not work.
We want to go after those hiding and going afk to leech, aren't we?
Another positive aspect, if you add such measures will be, that manipulating minis by letting one "friend" go inactive will get a bit harder, too.