Although that's a great idea, by adding existing guns to the setup, you are robbing people of all the money they have spent as well as like with all ARMAS guns, you are stopping them from being traded.
I feel that Legenderies from JMBs are an important aspect to APB as is rn, due it to driving up the Marketplace as well as offering unique solutions to weapons that are not *yet* available on the Joker Store.
Yes, people don't like this idea, yes some legenderies in the past were broken. But we are past the P2W mentality as it stands now. That said many players still think "Your gold gun noob, p2w".
As for "loot boxes being abusive", sure. but no one is forcing you to buy those. You have the option of the previously mentioned Joker Store or to straight up purchase a similar weapon from the vast catalog that ARMAS provides.
Loot boxes are just there as a alternative, that's just my opinion.
Don't hate, express yours.