Okay, I understand what you're saying now. If you're going to impose some sort of higher DA/MDA on yourself, to allow you an opportunity to have some control over the descent in an engine failure situation, that's not a bad idea.
It might, however, limit your options for destination and/or alternates. This is especially true for selection of alternate aerodromes and your "personal minima" could well result in the need to use an alternate aerodrome that is quite a long way away from your intended destination. All that extra flying, using one engine that has as much ability to fail enroute in that situation as in an approach scenario. Will you then apply the same personal minima to your enroute flying?
This could mean that you're going to be very limited as to when and where you fly because the weather won't always be as cooperative as your personal minima demands it to be.
To answer your other question... yes, when I flew SEIFR all those years ago (and was young, stupid and bullet-proof
), I was always prepared to go down to my legal minima as per the chart, adjusted for PEC and QNH - I was never in a situation where temperature was low enough to adversely affect altimeter indications. Thinking back on those days, there was probably only a handful of times when I needed the charted minima - most times, I'd get visual a couple hundred feet higher.
And the engine never even looked like failing on me whenever I was in IMC. It did, however, fail on me in VMC once or twice during my career. Significantly, those incidents occured greater than 1500 FT AGL.