Public test servers exist and could answer that in some form. Some players would even love that to preview content early. I’m sure there’s options and benefits to wider testing at some point.
Internal Q&A has nothing to do with public tests. Internal Q&A helps to find 99% of the bugs fixed during development. Public tests are done when the game is already mostly complete mostly for marketing, but also to verify some balancing tweaks or similar and detect a few extra bugs. And sometimes to do server stress tests
Internal Q&A can't be replaced with public tests. Internal Q&A testers working in the Bungie offices and outsourcing offices can be replaced by internal Q&A in other SIE offices (whereever they have their testers) and other outsourcing offices.
Big publishers normally have relatively small Q&A teams in their game development studios, and large global Q&A offices where testers are shared among all the games of all their studios. This helps to don't need to fire testers when games or DLCs (as happened with Marathon and The Final Shape) are delayed. And on top of that helps to share related knowledge among their teams.
But I’m saying having SIE have a dedicated team of high paid professionals that is used for Destiny, Marathon and concord etc… I mean they’re all online shooters? Is this possible??
Testers can test any game, normally don't need to be talented in a particular type of game or have special knowledge about that genre, because they have many cheats and debug options available to do their job, which isn't to play the game and have fun: it's to spot and properly report bugs, indicating as accurately as possible the steps/actions needed to reproduce that bug.
If Sony gets full control and ownership, they should cancel all Xbox support and delay PC releases.
Sony already has 100% control and ownership of Bungie since the day they completed the acquisition. Bungie is a fully owned SIE subsidiary. So they must obey whatever SIE mandates them and their main decisions are overviewed and approved by SIE. Even if they'll keep their publishing label and -like all other PS Studios teams- have creative freedom for their games.
One of the reasons of why they bought Bungie was to get money from the other consoles and PC, to increase the SIE revenue generated outside PS, so never wanted to make the Bungie games exclusive. Similar with MS's acquisition of Minecraft, Zenimax or ABK.
And Bungie recently underperformed in terms of revenue, so they need to increase their revenue. To cancel Xbox versions and delay PC versions would instead do the opposite, to further reduce Bungie's revenue, which would cause having to fire even more people.