In my mind, Turbos are expensive to buy, operate, and reduce the life of the engine.
That being said, I love my 2017 civic hatch with 1.5 Turbo.
The 1.5 is small, light, and has decent HP without the Turbo. When I need the extra HP, say to pass someone, I use it. But 98% of the time, I'm saving having a smaller, lighter, more fuel efficient engine. I'm hoping with limited usage, the Turbo will be reliable, and not too expensive to maintain.
The Hybrid system on the Insight is similar in that way, the 1.5 has decent HP on it's own, but light weight and fuel efficient.
The electric motor increases the HP from 107hp to 151hp.
So the electric gives you the extra HP boost already, and adding Turbo will add to complexity, but give limited boost as you are already at 151.
Cruising at highway speeds does not require a lot of horsepower, that's for acceleration, unless you are climbing mountains!