Nine seasons was enough. However, I would have preferred Season 9 to be a bit longer so the Cobalt Blue storyline could have a better development and closure.
Roy and Thea interacted too little with Team Flash, with the former not even appearing in the Flash show at all. While Felicity could have worked well due to interacting more with Team Flash, the absence of the other two is for the better, at least for me. However, a return for Roy and Thea could have been addressed in another episode if there was space for that.
The team was alright until Season 6 and even then there were issues with developing the characters outside their role in the team. You could give some slack then because the characters had good interactions and enough charm.
I don't really want to be a broken record over Allegra, Chester, Chillblaine or latter season Cecile and I'll just say they don't hold a candle to Jesse Quick, Wally West or Ralph Dibny.
Maybe if the whole situation didn't happen he could have hung out a bit longer and then move out with Sue.
The portmanteau would need too much attention. Zoom admittedly isn't the scariest term, but Demcer doesn't have that spark to really be used as an alias for a dangerous speedster.
The Rival's costume looks like a poor attempt to replicate the scary aspect of Zoom's costume. Granted, Zoom took his role as Jay Garrick's enemy, but even then he is almost forgettable.
For all its faults, Godspeed was scary since his clones were a bigger menace and early on he had the ruthlessness of other speedster villains.In Season 7 the clones wer scary when they were taking over the city.
We don't really need more continuation of Arrow. Oliver's story as Green Arrow is over and creating a Spectre show would require to come up with severe multiversal threats. it may even require several crossovers with other DC franchises and this is not really viable. Even reinventing Earths where the Arrowverse actors do doppelgangers of the main Earth isn't tenable.
It'd be best to do a different Green Arrow show, but it'd be best to use another actor to take distance from the hostile, gritty tone from the Arrowverse version. I wouldn't support a Green Arrow and the Canaries show at this point since it feels like more of the same.
Cicada and Godspeed weren't good villains. They started out strong enough, but the former had too little to warrant being an antagonist for so long and the latter was too bland and hard to take seriously.
As Zoom since while he was handsome then, he displayed his full depravity. The voice he had while wearing the costume and his murders are disturbing. A disfigured man that acts as a grim reaper of sorts is still scary, but he was only targeting speedsters.
Diaz is simply too tiresome and having him as an antagonist for the first half of Season 7 was too much.
Maybe 4 or 6.
Constantine or Wally are the most logical options for a show, as they could have benefitted from having their own stories and unique villains. Both got to work with the Legends, but could have had a better exploration that way. Cisco, Ray Palmer and Nate already appeared enough in their own shows and Khione really has no material to go off.
Khione has no appeal to really be a lead character, which isn't helped by her being too overpowered. The bad taste of Caitlin being possessed by Khione and not getting to bond with the rest of the team aside from the finale is not going to sell Khione as a character and otherwise she was just there to conveniently help beat the Negative Speed Force and to give a role to Chillblaine.
Well, Flashpoint was the reason why Sara Diggle was replaced by J.J Diggle. Barry's timeline alteration has some consequences in the Invasion crossover, but otherwise Arrow is not truly impacted by it.
It's just that the Sam Scudder and Rosa Dillion couple or the Weather Witch team never really worked for being underused. It doesn't help that Snart is a tough act to follow. The Rogue concept was okay in Season 9, but still too little was done with it in part due to the shortened time.
Wally was also wasted in Season 4. We barely got to see him fight without Barry's leadership or assistance before he was released from the Speed Force and his departure was very unceremonious.
COVID restrictions made it far harder to make crossovers not only due to requiring more people in a set, but the delays made it virtually impossible to coordinate for crossovers, let alone major ones like the ones pre-Crisis. Also, many of the Arrowverse shows were being finalized or cancelled by that point and it doesn't help that Superman & Lois decided to have a separate continuity.
Crisis had the intent of bringing new life to the Arrowverse shows by unifying most of the shows in a single Earth and forming the Justice League, but COVID really hindered that.
I simply fail to see a real reason to sell the Arrowverse to Netflix.
The suit looks better on Grant Gustin than Tom Cavanagh.
The "Barry disappears in Crisis" newspaper proves that Iris married Barry in the original timeline. Iris and Eddie might have only get involved due to Barry getting comatose.
A couple of spouses who wrote the Crisis episode where the Smallville versions of Clark and Lois return previously worked for Smallville. I don't remember their names, though. Caroline Dries also was involved with Smallville. Todd Helbing also was, although I don't know if his brother Aaron Helbing was.
It's kind of difficult since the series is in a shortened final season. It's even dubious that there would be crossovers with the core Arrowverse shows at this rate.