I love the idea of the BM archetype but I found it hugely underwhelming both from a gameplay and RP standpoint. I tweaked it as following.
The pet now scales to be roughly worth 1/4-1/8 ranger level in CR.
The pet is now bonded to the ranger. Not bonded as in "if it dies, the party makes camp, ranger sits in the bushes and is back with a new one before dinner", but bonded as in its death gives -2 Con and disadvantage on all rolls for the next week or two (grief), and requires a dedicated quest to replace.
Pet can be given commands that last longer than six seconds. Eg "stay alive" and it will move, hide, run, dodge, disengage, etc as appropriate. "Kill those goblins" and it will continue attacking the goblins until they're all dead. So ranger uses one action at the start of combat then gets to act as normal.
Pet only gains ranger's proficiency bonus to damage and attacks etc when attacking the same target as the ranger, or a target that the ranger has attacked in the last turn.
Damage to the pet forces the ranger to make a concentration save of DC 10 or 1/3 the damage to the pet, whichever is higher.
At 7th level, the BM can command nearby animals with 1/8 CR or lower to aid the party. Calls all beasts within hearing range to come to his/her aid. At 14th level this becomes 1/4 CR or lower. However, on any round where one or more of these beasts dies, the ranger has disadvantage on concentration saves.
At 11th level, the bond moves from spiritual to telepathic. The ranger can now command the beast to perform any action with a bonus action. (S)he can also cast animal messenger, animal friendship, and speak with animals once per day (or unlimited as rituals where permitted), as well as see the through eyes of the pet by going into a trance.
At 15th level, the ranger and his/her pet are bonded physically. They share a HP pool, and for as long as the total HP in that pool is 2 or greater, they remain conscious. Dropping to 1 HP causes one to fall unconscious (1d2 to decide). The ranger can end this state at any time, but it ends automatically if the pet and ranger are more than 60 feet apart. When it ends, each receives a percentage of the pool proportional to their contribution at max HP (eg pet has 50 max, ranger has 75 max, pool is at 80, pet gets 32 and ranger gets 48). While in this state they can only be healed by spells cast by the ranger, but those spells replenish the pool. Status effects that affect one mentally (confusion, charm, fear, etc) force the other to make a save (adv or not at DM discretion, eg charm person has lesser effect on a beast), but not physical ones (prone, restrained, etc).
At 20th level, the beast gains any attack and damage bonuses from Foe Slayer that the ranger gains.
I took a lot of the base class's stealth skills (vanish, hide in plain sight), etc and put them into a Stalker archetype, too, for what it's worth. These changes may well be OP, and my player who's playing the ranger isn't even 7 yet so I can't say, but it's the sort of thing they're cool with me tweaking on the fly so we're giving it a go!