As it stands now this is borderlining Pay-to-Win which is something that should be avoided. I don't care if its PVP or PVE players need to have a level playing field. Yes players who buy crown companions have more companions to choose from but it still maintains a rough parity because all companions are roughly equal. (Very roughly in some cases but I don't know of a single crown companion that dominates the game) however when you compare level Kobe 50 to his 52 crown companion version. There is a distinct advantage to the crown version. Yes of course it can be overcome if the other player is not as skilled but if players are of equal skill then Guy that used the exploit to break level cap is going to win.
Also when 2 players buy the same companion say at different levels 1 at say 48 and the other at 50. They pay the same prices but 1 player gets a superior product over the other one. And its not like the player who bought earlier can rebuy the companion or do ANYTHING to make that companion optimal again. Also keep in mind that it is not a linear progression on companion power. The gap form 50 to 52 is much Higher then say 30 to 32.
Also about the companion sharing I think after more thought being put into this that only Crown Companions should be unlocked or tradable across all characters when you buy them anything less then this feels a bit too much like being a Scrooge by kings-isle.
No matter how you look at it, you are talking on the basis of PvP, not PvE by making the comments like "borderlining pay-to-win", and "players need to have a level playing field".
In PvE, who cares what level other player companions are? You're fighting on the same team against the enemy, so the potential of high companion levels above L50 is moot.
This game is based on PvE. It's disheartening to think that the PvP mentality has reached P101 before it's even released, and the PvP people want to change the game for everyone, already.