With precisely the right conditions (some serious plagues, a significant change in scholarly thought, destabilisation of a major power, rapid dissemination of a technology that would allow for sudden and swift exchange of ideas such as movable type and several large-scale but not continent-scale wars) you can move straight from the 12th Century to the early 19th/18th Century in technology within 100 years. It's feasible, you just need to get everything right.
So if you wanted to get from Elbreth's Dark Ages to Renaissance tech quickly, you could have the Black Death hit the entire Storm Gulf, killing 30% of the population and rapidly destabilising most power structures. With the weakening of existing parochial authorities, heretical sects (the equivalents of Lutherans) spring up and use a new invention, the movable type printing press, to disseminate their views and spread other designs and ideas rapidly across the Gulf. Dozens of tiny wars spring up over land rights, leading to a very experience military engineer class that tends to move around wherever there is money, taking their designs with them (and probably a professional soldier class along similar lines). Amidst all of this, smaller trade companies destabilise the SCTG and break its stranglehold - the Guild collapses, throwing everything into chaos and leading to even worse war.
It takes about 100 years to balance out, by which time military technology in its various forms has advanced significantly and there have been some pretty sweeping social reforms as well in response to the violence.