I think that a sticker (or entry and signature) is always prudent, even if not strictly required, since it can avoid complications if somebody asks difficult questions in the future.
Subverting the conversation a bit, I wonder from the list:
VP prop,
retractable undercarriage
Turbo/Supercharged Engines
Cabin Pressurisation
Tail-Wheel
EFIS
Single Lever Power Control.
What's the maximum number of those you can manage to require on a single aeroplane?
My personal record is I think only 4 on one aeroplane (VP prop, retract, turbo and EFIS) on a G1000 equipped Turbo-Arrow, but there must be aeroplanes that require more of them at once?
Any advance on my four?
G