adding additional curners to steam boiler

My Slantfin 120,000 Btuh (90 + 30) steam boiler has room for additional burners. I am contemplating adding radiation (both on the steam system and possibly an additional basement baseboard loop circulating condensate. Of course, I will use a pro for this - but I am interested in gaining some insight into the pros and cons of various options, hoping an intelligent customer is appreciated and not viewed as a pain in the neck!

So... I assume adding burners (but keeping all pressure/temp controls the same) will allow the system to steam faster, especially if the condensate loop is circulating water while upstairs calls for heat. What's the downside, if any, of adding burners? I guess the flue is optimized for a certain rate of combustion...but is there something else to think about? Efficiency? Is it possible to generate the steam "too fast"?

Also, are there controls that can handle dual configurations (steam with an auxiliary hot water zone) in an intelligent way? Maybe I'd like to prioritize the main upstairs heat over the auxiliary basement so the latter doesn't operate when I'm calling for steam...

I have a small Cape Cod with a one-pipe loop in the basement. I am adding 800 sq ft to the main floor over a basement extension. I would like to add the required radiation - while downsizing some existing that will be replaced by smaller radiators once the room becomes an interior one (no outside wall, doors or windows). Then I would like to put a baseboard in the new basement. My basement main is presently uninsulated (that's how I heat the basement). I have also removed some radiation years ago... so I think I should have capacity for the extension; and I can play with the pick-up capacity (especially if I replace the insulation on the main, which was removed asbestos).

Anyone have experiences with this type of arrangement? I would love to know how it worked out.

Merry Christmas.
Gary L