+1 OP !
1) I agree that a beast master pet should not be summoned. Simply because beast master pets in 5e are not summoned - they are there, constantly. And managing them is a part of your character design. In this particular scenario, I would ask Larian to take a look at Owlcat's pathfinder ranger pets and make something similar.
2) If your beast master pet would die as a ranger, there is literally a mechanic within 5e for this: "If the beast dies, you can obtain a new companion by spending 8 hours magically bonding with a beast that isn’t hostile to you and that meets the requirements." (the requirements being the following: "Choose a beast that is no larger than Medium and that has a challenge rating of 1/4 or lower") - both quotations are from PHB. Of course, I believe that a beast master companion should, like JandK mentioned above, be able to be resurrected in the same ways as regular party members - but there should be an option to tame a new creature if the pet perishes as this is listed as an available option according to the PHB.
3) As I've started playing a lot of PnP DnD, I've realized just why the DnD veterans on the forum (and in general) are a bit salty about rangers - not just in BG3, but core rangers in general. Compared to the alternative sourcebook specs, such as Swarmkeeper (my personal favorite), Fey Wanderer, Gloom Stalker, Horizon Walker and even the brand new Drakewarden, the core ranger specs just falls flat. They do not only deal less damage and have much more situational damage on top of that, but their utility is often much worse as well (especially when translated to a cRPG where food gathering, foraging, night watch and terrain orientation is not required). I am sad that Larian has decided to "dedicate themselves" to the PHB (although they homebrew a bit too much for that statement to be accurate) as that kinda makes ranger just... Bad. This is a known issue among the DnD community since the core ranger specs are considered memes at best.
In general, I am quite certain that BG3 will develop to be an AMAZING game. I just hope that Larian can find a way to make the core ranger useful. It feels really bad playing a spec and knowing that I could have picked at least two other classes (namely fighter and rogue) and I'd literally be able to fill the same role and perform the same, or better.
Anyways! I do hope Larian do reconsider regarding expansions/DLCs as I would love to see some additional sourcebooks being added eventually. Until then, imma grit my teeth and do my best to love my core ranger. <3
