How do you feel about a "Normal Procedures" takeoff?
In the first instance, quite obviously, I can't recommend it.
In any case, I prefer to follow the POH data and OEM recommendations
and they fly the chart speeds every takeoff and landing.
Indeed .. and I really can't see why the light aircraft can't be operated with a similar philosophy ?
I'm not sure whether you're recommending flying the performance chart speeds or the recommended speeds? They are different.
Cessna seems to have recognised that most of the time, the 172 will be flown off more than adequate runways.
When the is doubt about runway length, they assume that short field procedure will be used and that is what they use in the charts. But they do not recommend short field procedures for normal operations - the normal procedures presumably have more safety margin.
Cessna also seem to assume that pilots are smart enough to figure out when runway length might be an issue.
Where do CASA's declared density altitude charts fit into all this, they don't mention temperature?
I think they are an historical anachronism which hasn't yet been consigned WPB, round.
What temperature do you use for performance calculations when operating into a location without a forecast?
One ought to be VERY cautious when it comes to extrapolating temperatures .. OAT affects both airframe and engine and, in the absence of specific data relating to both, especially the engine, it can get rubbery .. quickly.
It's just the laws of physics, and they are in fact well understood.