I haven’t had to deal with it…but I love pet classes in video games…same way. Creature is fully independent, not a PC. Not an NPC but a creature controlled by the GM at the PCs whim.
Will do what the PC commands,
Attack that guy
Jump over this wall.
So on and so forth.
Each command is an action of the players.
How the creature responds to the command is up to the interpretation of the GM…and they will continue doing that command until told otherwise.
Odd things ensue.
Attack that target… Wolfe attacks the target…target dies, Wolfe continues…perhaps even eating said target.
Player gives a complex command to Wolfe. Attack that guy, until it’s down, then go to that target till down, then that target…
Wolfe attacks the target…target dies, Wolfe continues…perhaps even eating said target.
Attack the target I engage with…player then casts a spell at a target…Wolfe sits there watching for his master to engage a target…
You get the idea. The companions contribute, at the characters command.
Let’s say the companion is a squire or apprentice…much larger ability to comprehend and contribute…but also apt to do something different then the command depending on motivation. The companion is an NPC loyal to the PC at that point. Or disloyal.
If PC controls a large number of creature say in the aspect of a necromancer. Loot that allows for 3 commands per action or D4 commands per action is in order, or a group command might be given.
I’d also have the creatures go just before or after the NPC turns…but in a big battle that might be too much for the GM to track, so companions respond instantly to the commands.
Also, find out how the PC commands the creature. Magic?
How does the magic manifest? Impulse control?
Preset verbal commands?
This should give the PCs with pets enough coolness points, but not double actions. It should be a happy medium.