Red hollow Triangles aren't exclusive to "Open Play", although it's only a little Detail.
My 2 cents :
In my books, it's entirely up to the Developer - specifically NOT Players operating within - to provide certain risk levels.
If only Players could bring risks, then something is terribly wrong. To an extent, that's unfortunately the case, as the Game suffers from multiple design flaws all combining.
What Open Play delivers as an exclusive is the unique experience in hotspots. That's what defines it.
However, that comes with a broad mix that clearly isn't for everyone.
Friendy, Boring, Hostile, Deadly, Toxic, Unbalanced, Buggy, exciting, nerve-wrecking, "meet the Idiots", "meet funny guys", "meet the Ganker Wing", "meet the guy(s) who work to save your Ship", the "Silent Bob", the "Chatty one", the guy you ad-hoc Winged up with in a RES and become friends, the guy who ad-hoc blew you up in a RES for Lulz and possibly ends up in your block list.
It's all there, all at once. Like a box of chocolate - you never know what you're gonna get.
Thing is though : That experience is the Reward of Open Play.
That's it, no bells, no jingles, just the occasional close call, some annoyances (chain-interdictions/lulz folks in suicide-winders etc.), some delays (blocked Pads anyone?), a few Exploiters/Cheaters, maybe PvP Kills to your count or Rebuy screens respectively.
Sometimes though just as empty as Solo.
That's the incentive for choosing Open Play.
And in the nightmarishly unbalanced world of ELITE PvP Combat, why (other than by personal decision or RP) would i.e. an Explorer with 6 months worth of Exploration Data choose Open Play to fly to a CG hotspot and hand in?
Lose 6 months of hard work to some other Players in G5-modded Meta Ships, experience the wonderful world of Ganker-Weaponry (Shield-killers, Shield-breachers, FSD Disablers) within 10-20 Seconds for lulz?
That's one of the issues with ELITE, since it sometimes isn't just the Ship. Screw the Ship, that is replaceable - but the Data is not.
"Balancing" Open Play IMHO would mean downright fixing it (redesign) for good.
BUT... that'd drastically affect Engineers, literally remove quite a few Weapons and many Special Effects, plus alter the Combat System and run different Insurance models (Data or Cargo-based). Likely even providing an alternative way to travel inside a System.
Unsure on how many feet such a drastic move would step on, but I guess it'd be quite a few.