So the hardest part for me to deal with here is that you are trying to tell us you got the tiger purely to carry your gear. Not a horse or a mule, a battle tiger. You happened to select a 6hd mount, bought it armor and a combat sable and it is only to help out with your carry capacity. You got it to be a combatant, its the only reason.
Do you ride this mount into combat, casting while mounted with zero mounted combat feats? No Animal Handling or tricks? It is not a companion or a familiar either..How do you stay mounted when it grapples and rakes? And why roll HP is it is just to hold gear? I am betting you are not mounted and it is used as an overpowered companion.
This is an example of a player coming up with a backstory to justify campaign breaking. Cash trait does not make up for some jacked up companion. The tiger did not break the campaign, the player/GM combo did. You claim total innocence and feel others might take advantage of this trick you found, sounds more like bragging.
I am surprised the GM and no other character called you on this, must be a new group of players. Talked to my core group of players/GMs about this and not a one said it would slide. I will give you props for coming up with the idea, just wouldn't allow it.