Checkboard,
Your logic is correct if you are using "improved climb" as a way of increasing takeoff weight.
"Optimized V-speed Takeoff Charts" are a different animal altogether, in this case there is nothing stopping you from using assumed temperature or a derated thrust with "improved climb".
Lost Soul,
Paste the "offending" parts of the chart on here and we can have a guess at it.
Cheers
Mutt.