Double NAT, online gaming (Blizzard) and pfSense

[n3mmr]

We're a condominium doing our own internet access delivery: we have a business style subscription for 1Gb/s, we share that to all our tenants, using private IPs in the 10.0.0.0/16 range. This sharing is currently done using an old ZyWall usg2000 as a condo-wide NAT router.
Each tenant is supposed to connect a private NAT router to the condo intranet, and they're not supposed to use bridging or UPnP or PMP in the private router.

Online gaming to Blizzard games and any game using STEAM services are plagued by short fails at irregular intervals: at intervals of anything from ½ hour to a day or so, mostly centered around a few hours, return traffic from the game server goes silent, like something drops all those packets, fir 5-10 seconds.
Different players behind different private NAT routers experience this quite independently: one player may have interruptions 5-6 times in a single day while others get the problem only once, and there's no obvious interdependence.
However, if the player uses, say,Teamspeak or Discord conferencing to talk to other team members, that connection breaks in perfect sync with the gaming break.

Suppose we replace our current condo-wide main router with a modern pfSense router, what could we do to improve the gaming experience for our tenants?

[Derelict]

Get an IP address allocation, a layer 3 switch, and give each of your tenants a /30 (or more) and let them worry about their own firewalls.

Kind of like a real ISP.