Failed steam boiler and chimney too small to vent

Hi

I have an 114 year old New England house that has a steam boiler with single pipe steam radiators which I bought a little over a year ago.  (Natural gas.)  The 30 year old steam boiler has rusted through and needs to be replaced. However, the chimney which it and the new gas water heater are venting to is too small and it is not fully lined - the chimney is partly split and could only be vented with a 3 inch vent - without insulation.  (Unfortunately I was not told about this problem when the house was inspected or when the boiler was serviced last year or when the gas water heater was replaced in this April or I would not have been doing this in the fall.) The chimney experts all agree I can't vent a new boiler in the chimney as it is too small. So that leaves me with several options. (Rebuilding the chimney is not possible right nowi).

the options seem to be:

1:  Install a class A external insulated chimney which would attach to the side of the house and the metal roof with brackets and install a new steam boiler (Burham Independence model or a Weil McClaine) and use the existing steam radiators.  The chimney would need a special piece to vent both the existing water heater and the new boiler.  The location of the chimney would be right over a walkway leading to the main door of the house and would be very visible.  The bracing would have some kind of angling behind it on roof to divert the snow. (My metal roof is really good at losing snow). As in nearly all options, the venting would have to be through a brick foundation and a secondary decorative stone wall foundation. I haven't been able to find a picture but I was told it would be shiny stainless steel.  Aside from looks, biggest concerns are snow coming off the roof and snow building up around the chimney itself. 

2. Install a steam boiler that can power vent out the side of the house either through a basement window. Meaning the window would have to be removed and covered over with pressure treated plywood which would be ugly. This contractor said I would have to remove my gas water heater because it can't be vented through chimney and install an electric one.  (City won't allow only water heater to vented this way).

3.  In talking with another heating specialist, I think I may have another power venting option of power venting a boiler out the foundation wall and power venting the existing water heater.  It sounds like this requires two different power venting locations as they can't vent near each other  (or the windows above the two basement windows).  I don't know if this saves money now but adds parts (fans or blowers that fail) that could be expensive to repair.

4. The last option would be install a high efficiency heating system that uses hot water baseboard. That would have an intergrated water heater as part of the system so only one hole would be needed to vent out and it would not be power vented so no mechanical power vents to fail. It would however require removing all of the steam radiators and black iron piping running all over the basement and replacing them with baseboard throughout the house. The steam pipes were insulated last year.  This would allow for multiple zones. it would however mean losing the radiators.

Some radiators are on inside walls, some on outside walls.  It appears that at some point some may have leaked as there is damaged wood where the pipes are.  However, I can't tell if they were fixed or if they stopped because of the leaking boiler (eg there really isnt much steam in them anymore)  There seems to be new parts on some of the them.  They did not bang or clang at all.  Aside from the themomstat being along the wall with the chimney was and therefore being a warmer location, the system did seem to work last year.  It would take about 30 minutes to get all of the radiators to turn on and sometimes the system would shut off before the heat reached the last radiators because living room would get warmer faster and the system would shut off.  I like having radiators but I have no idea how well they work (eg leak or not) if the boiler was working properly. 

What advise can you give?  What option would be best?

Thanks for your help!