not if "in combat only" once you have more than two of them they are treated as a horde/army.It screws up combat
It screws up combat
It screws up combat
It screws up combat
It screws up exploration sometimes.
The player would have to agree to a social contract not to go through all the tactical options of every zombie not abuse having extra chances to do a lot chance option.
out of combat they carry the box.
Not sure how it makes other people feel, but we have tested it, and we think it great!
Out of combat: carry boxes, dig, guard perimeter, row undead boat, etc, use stat block for undead creature.
In combat: two ghouls? Run as normal. Four skellies, convert to swarm.
In or out (depending on how many encountered): sneaking past their guard line? Stat Block. Made lots of noise and failed to sneak in? Use swarm block. Skellies in mass? Difficult terrain. Angry Swarm? Swarm block.
Grapple on skel versus one player? Stat block. Horde of skellies grappling: Swarm block, one of its attacks is a grapple, other attacks as normal or on grappled creature at advantage.
Etc etc.
Players use these guidelines, and I use these guidelines for the evil necromancer.
Sweet and neat.