And while I'm thinking of things [;)] it would be cool if the settings for the stair are stored in the created object, so you could reopen the dialog, tweak the setting for that stair object, then update/replace it. This would allow easier experimentation. I found it hard to configure an exact 180 degree spiral for example.

That would be a great advantage while designing the stairs. It's something I also wish could be done with the Generate 3D Shape tool: right click the shape and read it back into the tool window. For the Staircase Generator it might be even more desirable.
Maybe the best option is to have a function to save the configuration to a file and have the option to read back such a configuration (i.e. save as <staircasename>.scc StairCaseConfig). Such a workflow could be used for similar generators as well.

Regulations differ per country/state so it's impossible to incorporate them by default. There are even different rules depending on the place and function of the stairs. I did some heavy research when I designed my public staircases and I tried to stay as close as possible to the most common regulations for public staircases, which differ greatly from the regulations for home staircases.

I suggest that anyone who wants to stay close to the regulations for his country to just look them up and use them as a guide line to create the staircase. The most important ones are min/max sizes of threads and risers, the min/max depth of the staircase for a set elevation (i.e. the number of threads before a landing is required). One 'advise' for public staircases I didn't follow was adding a nose that extends over the previous thread. That's not advisable for public staircases for safety reasons. That's also why you can make them invisible [:)]

As it is the Staircase Generator plugin is great. Any finetuning can only make it better.