Re: Solution to address 3rd partying and teaming up in solo mode
@Koochi-Q Apex doesn't state anywhere that it is forbidden to team up in solo (like pubg does in its rules of conduct). This way, it leaves the solo thing to interpretation. you start as solo, there can be a sole winner, etc.. Also, I don't think there is a written general set of rules for the battle royale genre and it would be bad to not allow creators to think outside the box and come up with original interpretations.
Anyway, the idea that I suggest may sound really odd, hard to grasp. But the experience in Destiny 2 proved how smooth it can be to transition from a public area to an instance available only to you (and your teammates) and provided an interesting way to lock events in the public area, while Titanfall 2 demonstrated how amazing it can be to jump between different instances of the same map.