Here's the rub. HVAC company probably told them sometime like $18-20k or even more.
When hit with a number like that, it's very easy to overreact - screw that, I'll go all elec. - not realizing that if you were to upgrade their service and outfit the whole place with base heat and wall stats, they're gonna spend more that way. Radiant heat, too.
One thing to consider is that you most likely need contactors for each room because you'll exceed the wattage of an inline stat real fast. Unless they want dial stats on the units
Here's my suggestion, based on my experience:
I had a free estimate for a very small house (564 sf) for 1.5 ton heat pump w/ 8kw strips in the air handler. Reusing line sets, and me adding electrical for furnace. The price was $9,100
You know what I did? I found my system on eBay for $1,400 so I know that HVAC company wouldn't be paying any more than that. Even if they marked it up 50% that would be $2,100
That means they wanted $7,000 for 6 hours of work. You know, ain't no construction worker getting paid $1,200 per hour at my house.
I bought the units, and hired my son for $600 to install them. He was done in 6 hours. And with what I paid, I could do it 3 more times and still cost less than HVAC thugs wanted.
I would suggest to that customer to buy the units online and have a Craigslist guy install them. Even if they shoot craps, they can pay someone to fix it and still cost less than half.
HVAC thugs are like - but but but you'll lose your warranty.
Who cares, if you can pay out of pocket 4 times and still cost less?