Yeah Cease isn't an ace at the moment but he has the potential to be an ace if he puts it all together. Getting out of Chicago helped and hopefully now with the Jays system, they can help him work towards that.
This signing kind of reminds me of when the Jays signed AJ Burnett during the 2005/2006 offseason. Burnett at the time was at a similar age and more of a No. 2 throughout his career, though had the stuff and all the potential to become an ace. The only difference between Burnett and Cease has been durability. At the time, health/durability was Burnett's issue as we saw in 2006 and 2007 he only made around 20-25 starts each of those seasons. Though in 2008, he pretty much developed into that ace Toronto envisioned during his opt out year lol, posting a 5 WAR season. Sucked with the Yankees after, though put together some solid years with the Pirates.
The plus with Cease is durability and a healthy track record, so you know he's good for 30+ starts and around 170-180 innings and likely a floor of 3.5-4 WAR, which is still very good. Cease has the potential to turn in a 5-6 WAR season if he puts everything together and that is exciting!