add a loop on steam boiler

Snowmelt

about a month ago I added a loop on a steam boiler to heat an addition of a home with 2 water rad. ( this was my first attempt at this.) Now my mind is really thinking, I followed the diagram which i found on line and my supply house gave me to go by. It works well, have the aqu stat shutting the boiler off so it doesn't go into steam but the pump stays on with the T-stat.
MY mom has oil and I want to change it over to gas, the contractor before I know I was going to be in the heating trade didn't really do the add a loop correctly , also mom has a domestic coil in the boiler. i also added a snow melt system for driveway and made the kitchen and back TV room radiant. I have 2 questions for you guys and tell em whats more economical.

1 should I get a steam boiler with a domestic coil , and a loop for an existing baseboard and get a small 30 gallon indirect to run radiant .
2 no coil maybe a flat plate HEX and run 3 zones 1 for baseboard 1 direct water heater and a zone for radiant .
3 run the radiant right off the steam boil ( but I am worried about condensation back to boiler. ) also run a zone for domestic and a zone for BB.
any other options ?'
( the snow melt is on a tank-less water heater with radiant floor right now, when I added the snow melt is when the gas company brought the gas to the house )