This would help to fix PVZ without breaking PVT
PVZ is extremely difficult and one of the main factors is how easy it is for Zerg to snipe detection in the lategame while using lurkers and spore crawlers making your completely shutting down your attack just by sniping observers.
Oracles work but very difficult when you have to micro sentrys + templar + mothership + split vs a Zerg army which can destroy you with 1 parasitic bomb so you also have to constantly split.
Proposal reduce Observer build time to 15 seconds and reduce cost from 75 gas to 50 gas.
Should help to balance PVZ which is much much harder for the Protoss player right now.
In compensation for Terran slightly buff the build time of banshees by 10-15 % which will also give Terran more proxy banshee options vs Protoss which already has proxy oracle and is slightly favoured in the matchup.