If Power Play is made open only and the winnable toys aren't made available in other ways to those in PG or Solo then a good proportion of those PG and Solo players who want to win those toys will play in Open but will find other ways to avoid PvP interaction.IF the game was such that all vanity items in the game were earnable by doing in game stuff and every feature and each faction had their own paint jobs and ship kits etc and we had some form of in game trophy cabinet where we could see all of our unlocks - a bit like the bobblehead wall in fallout (which is exactly how the game should be imo.;..... i would have immense fun just trying to "get them all" ) then i would have no issues with PP having its own cosmetics even if in open only. (i would probably just log into open, do PP and get the skins before bailing but that is by the by)
however the game isnt like that, so what you are suggesting is making PP a special snowflake feature which would be the only feature which rewarded the player with skins and trinkets..... and that I am less in favour of.
And there are many ways.