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Steam does have its points. I've restarted two pipe steam systems from cold, down to about 10 F temperature in the house, though just barely at freezeing in the basement. It's a bit tricky… but doable.

And… in ordinary situations, where the system hasn't been turned off, a steam system will just turn itself back on after a power failure. You don't have to do a thing.

More propane heaters and a wood stove. Without reliable electric power it will freeze with any other option.

STEAM, All you’d have to do is drain the boiler 😎.

One other strong recommendation. Very strong. Hire a local (and pay him or her, dang it) to come and really check on the house when the power is off (and, preferably, regularly anyway). Whatever heat source you use.

Why people won't do that baffles me completely…

This. And a steam system can be built with a minimum of moving parts, aside from what's on the boiler. See:

https://www.heatinghelp.com/systems-help-center/european-heating-systems-circa-1907/

I'd prefer something you could restart remotely.

Do you want the hydronic system back in working order. Comfort to many is superior to forced air. Although FA will recover quicker. I would not drain and refill a hydronic system. that allows excessive O2 into the system. You would probably need an air compressor to get 100% drain of the piping if it is fin tube.

Cheap and maybe easy would be a mini split, or two.

Drain the water system when you are gone. Heat cool, efficiently with mini splits.

Wood stove for back up/ power outage and quick heat

The right answer depends on your budget. My recommendation is ALL the below:

Non condensing propane furnace.

Heat pump. Size the heat pump for cooling, not heating

Compromise the performance of the ductwork (a little) to keep the aesthetics. Hardest part of the project, but you will want the AC.

5 to 10 KW propane standby generator with battery bank backup. Check out Generac PWRcell. Pricey, but maybe competition will bring prices down. The batteries in the PWRcell are more than you need. $500 of deep cycle lead acid might be enough.

Cellular Internet and and cameras.

Maintenance contract with Generac Installer and/or propane company.

Shut off well when you are away. Maybe drain the domestic water pipes.

Southern Indiana is a humid continental climate. Some colder winters and many hotter summers than New England.

If it were not for your power supply problems — which are much more common than some on The Wall realise — my suggestion would be a heat pump. You say the climate in southern Indiana is extreme… well, not really, and a good cold climate heat pump should be able to manage. Depending on how large the house is and how it is laid out, you could either use one or two mini-splits, or a central unit. For the latter, you would have air ducts — and my suggestion there would be to admit their existence in the various spaces. Architecturally, that would be preferable to attempting to hide them — which never works well.

However. You do have that power supply problem, which means that the house is going to freeze from time to time — and despite the wonders of the modern internet, you won't know about it. The problem is that an auxiliary generator big enough to power a heat pump is going to be a fairly good chunk of change, particularly if it's automatic.

I think that my approach might be to really evaluate the existing radiators, and replace any which are too badly damaged to use and also replace any suspect — never mind burst — plumbing. Then use an appropriately sized propane fired boiler to provide the heat, and use glycol antifreeze in the system. That could run off a much smaller generator for when you are there and the electricity isn't — the antifreeze in the heating system would allow you to fire it up, no matter how cold it was. You would still have to drain the domestic water plumbing, but that may not be that much of a hassle.

I would drain down the house and turn the heat off when you're not there.

If you put glycol in a hydronic system it won't burst even if it freezes. Forced air doesn't need any special protection other than perhaps a splash of gycol in a condensate trap.

Do you have internet access? It's nice to have something you can turn on half a day before you arrive so the house is warm when you get there.

Generally the house plumbing is a much bigger deal than the heating system. I find it easiest to blow everything out with compressed air. If there are fixtures that aren't frost-safe even when blown out, over time you'll find them, just replace them.