Parmandur
Book-Friend, he/him
So, then, yes. Got it.
Not interested. The other features are great, but the beast master subclass is underpowered and fails at making a companion that fights beside you. If they aren’t willing to directly address that, instead of trying to make us choose between having spells and having an effective companion, I really don’t care if this ever sees publication.
The Beastmaster is properly powered for what it was designed to do, have an expendable pet that helps in exploration and somewhat in tactics: there is a mismatch between what the design and what some people want to do with a pet. Mearls goes into the math of spell slots, damage and HP in combat. The current Ranger is about right in power, but complex and fiddley. Giving a Ranger half-casting plus an effective pet plus combat prowess would be ridiculously OP.
This new design gives a pet that uses all of the math of the Ranger spell slots to achieve full effectiveness, while letting the Ranger be effective separately. In essence, the build-a-beast is an incarnate stack of spellslots, taking and giving damage.