If I recall correctly, the certification basis for FIKI in light GA aircraft was introduced in the late 70's (1977 or 78). Therefore, planes with de-ice/anti-ice equipment built before then are not officially FIKI but have essentially the same practical capability, which is to say, they allow operation in light to moderate icing conditions for a brief period of time, allowing the pilot to escape the ice before the aircraft is overwhelmed. My experiences flying light twins with pre-FIKI and FIKI systems is that they perform about the same (except for the windshield).
For the 310, the "full de-ice" system is heated propellers, pneumatic boots on both wings outboard of the engines, pneumatic boots on the horizontal stabilizer, and an alcohol sprayer on the windshield. The FIKI system adds pneumatic boots between the fuselage and engines, I think adds pneumatic boots on the vertical stabilizer, and replaces the alcohol sprayer with an electric heated windshield. I think that the same general differences apply to the larger Twin Cessnas.
As I point out every time it comes up, those differences are not enough to change how I fly. If I am picking up ice, I am changing altitude or heading to get out of it rather than hanging out for an hour because of a minimal FIKI certification. (Frankly, although I am not qualified to fly them, I suspect that I would take the same approach in turbines. All that power is there to get above the weather, not to push through it.)
Right.
At the moment, the two that seem to top the list are the Twin Comanche and the 340. The piper seems to have significantly lower operating costs; the Cessna looks more family-friendly.
Either can be acquired for less than a SR22T.
Of course, MESL certification is a hurdle, and the operational and maintenance complexity is not a small differential.
The AMEL rating is not a hurdle in any meaningful sense. There are two kinds of twin-engine airplanes:
1. Those in which you can get your AMEL rating without hurting the airplane, such as a Twin Comanche. The insurance on these will require about the same number of hours of dual instruction as it will take you to get the AMEL rating.
2. Those in which you will get arrested for airplane abuse if you do extensive single-engine training in them, such as a Cessna 340. The insurance on these will require in-plane and initial simulator training and the premium will be high enough that the cost of getting your AMEL rating in a rented Seminole will get lost in the noise.
Very few people who have owned twins would recommend that the first airplane you own have multiple engines. It's not impossible, but the safer and more affordable path to twin ownership is generally going to be by way of owning a single-engine airplane for a while.