As Enkidoh said, your GLD/PLD is level 37, and it shows that you have no clue what you are talking about.
1st: The current ex trial "one of many" examples? Invuln for emergencies? You certainly have no idea just how powerful Hallowed Ground is outside of casual content without any downside, maybe except its CD which you play around with your co-tank. HG and Superbolide negate any damage income which means they can tank stuff without getting any debuffs like dmg downs or vul stacks. It's invaluable in savage raids, e.g. P4s part 1 and 2 mid fight tb, O7s tethers, or practically any tb with debuffs. Also, LD and SB are anything, but "too short"; there are barely any tb timings DRK can make use of LD more than GNB, but WAR is the only exception. And even then GNB gets barely more usages of off SB than PLD off HG. I don't know what you are on about with the current ex trial when you haven't even reached EW levels... your assumption that "this carries across every encounter [...] since 6.0"/6.x is also just wrong! Where did you even get that impression?
2nd: Ofc it breaks PLD rotation! The current iteration of PLD rotation leaves out 1 stack of Sword Oath to keep a ~61s rotation on repeat... that's 1 skipped GCD. Your suggestion is to remove 2 (!) GCDs from PLD rotation plus a dot duration reduction. You will fall under 60s every circle because you can't - and do not want to - avoid SkS on your gear/melds. A dot duration reduction will lead to it falling off during your Req window, too. Study PLD first before you claim your suggestion wouldn't cause any issues.
3rd: PLD doesn't have a flexible rotation? Then what about this?
This isn't your simple 1-2-3-1-2-4-5-5-5-1-2-3-caster burst stuff rinse-and-repeat stuff. Compared to other jobs this is rocket-science level. E6s is another example how good PLD is designed; it's possible to keep 100% uptime with Requiescat during tornado phase (you must disengage from boss). Something unique and an adventage over any other tank!
"Any loss of uptime [...]" Well, guess what: most jobs have this "issue", mostly melee jobs. PLD at ~70+ even has the choice to use Holy Spirit should they deem it necessary, it doesn't even break combos. What do you think GNB and DRK, or any other melee (e.g. MNK) will do? Either nothing or hit their low potency ranged attacks... that's not even an argument. Your goal is too keep uptime as much as possible; if not, use your tools to your advantage. PLD has more options than any other job in that regard!