1 - I think critter capture pets should be a rep grind. However, I think that the rare variants (the huge ones) should be pay shop only.
2 - I think this is a great idea!
3 - I believe that those boss pets should either drop rarely from the boss themselves or should go into the achievement shop after doing some sort of hard challenge involving said dungeon. As for trickster, I think that should also be a rare drop along with the token. (And of course since its PVP, the pet should be tradeable so it is also dropped in PVP)
All in all I think pets are more dram sinks is exactly what the community needs right now. I know many people are just looking for another excuse to keep playing for hours and grinding stuff out. And it shouldnt be too hard to implement given all that has to be done is appropriately sizing said creatures and also giving them a walk cycle (which most already have) and petting anim.