powertop-1 and -2 are very different programs, please consider a slot'd version 2, to have both versions installed on the system.
Created attachment 316107 [details, diff] ebuild patch install powertop-2.0 as powertop:2
Just hint, do not mess with names on install. Use the --program-suffix=2 on configure phase. It is standard configure option.
Is this REALLY needed? At this point powertop-2.1 appears reasonably usable if you enable the kernel options the ebuild suggests.
I asked two months ago if this was really needed, no one responded. Closing. At some point in the future when powertop-2 is more usable I may consider it but right now I can't say I see the point.