Having flown with about 7 or 8 different instructors none of them ever mentioned anything about letting the engine warm until my IMC instructor just made a comment about it in conversation.
Did your aircraft flight manual say nothing about oil or engine temperature in the green prior to takeoff?
I fly in a MC invironment. We spend a long time checking the aircraft and all the other things required before the flight so that the aircraft is ready to go when the PAX arrive.
What is an "MC invironment?"
It took a while before it dawned on me that there was no reason at all that I could not do the power checks on the apron instead of the hold, the way the aircraft get parked means there's nothing to get damaged, pre take-off checks (take no more than a few seconds) still done at the hold or on one of our runways the hold point is so far away from runway they can be done when rolling to line up.
I encourage students to do this just prior to entering the runway, or where practicable, on the runway itself.
Checks, particularly carburetor heat checks, should be done as closely as possible to takeoff. The check isn't just to verify an RPM drop, but to ensure that any carburetor ice is removed. Mag checks verify not only that the P lead is connected and the switch contacts good, but that the mags plugs haven't loaded up and we dont' ahve a bad magneto. It's very possible to have a good mag check on the ramp at the parking spot, and have the engine die during the takeoff from carb ice or fouling because of developments during the taxi time to the runway.
One slow speed which can give the PAX the idea that you are such a bad pilot you need a guide to fly a bit like the German pilot in those magnificent men and their flying machines with a how to fly an aeroplane hand book. He was fine until the handbook blew out of his hands and stuck on the tail of the plane where was he then??? He had to climb out and retrieve it)
About a year and a half ago we had an explosive depressurization in a Cessna 421 when the windscreen failed in flight. The top of the instrument panel, glareshield, and some of the interior disappeared out the window. The glareshield was outside the airplane, in front of the windscreen causing buffeting and vibration. The checklist was on top of the glareshield, and after the event, was nowhere to be found. It's probably in a farmers field somewhere, now.
I don't know what you're trying to say with the "one slow speed which can give..." bit, though.
On occasion because I know my co pilot well and the aircraft very well I will run the checks from memory while getting the co to read them out and visually check the items on the move. We still confirm those items.
The point I am tying to make is that as a pilot there are occasions when you have to up the game and knowing not just the aircraft but the check items facilitates a smooth, prompt operation.
That's the point of doing flow checks; do the flows, then read the checklist.
I still hold with the fact that there are occasions on the ground and in the air where knowing your checklist from memory with the checklist as backup is a far safer way than letting the aircraft run away from you and other events overtake you.
The times when you should be on page 4 of your checklist not page 2
If you have a four page checklist, then you have a problem. Get a better checklist.
Memory and stabilization items should always be accomplished without need for a checklist. Once the situation is stabilized, especially in an emergency, one should absolutely proceed with the checklist, and one should read everything, including the stabilization items already performed.