The submission is largely about improving cricket in the ACT - they say they punch above their weight already (10% of contracted players are from the ACT, apparently), but it makes it harder for Canberrans to make cricket their focus when facilities are so poor, and so they either leave the Territory or give up. Having equal membership status brings in more money for that purpose. And having BBL and first-class teams in the ACT will further drive the sport in the territory, which brings more players into the pool. It's basically the same argument as was used for Tasmania's entry into the AFL.I don't think the talent pool is deep enough to add another team. The standard of cricket is already pretty questionable with some of the grade cricketers and "international stars" on display.
There are enough players out there. Take Matt Kelly for instance - takes two wickets in last year's final, and then doesn't play at all this season. Another team gives more opportunities to new players coming through the ranks - AJ Tye had been rolling around grade cricket for years, and within two years of playing his first game for the Thunder, he's playing for Australia.
It's hard to find any metric to justify an argument about "the standard of cricket", but it's worth noting that there's a window for the test players to play BBL for the next two seasons, which will improve the talent pool.