So all this sounds like an excuse of please bring back the shitshow for the last 5 years of no balance and people crying and bitching cause their favourite tank is being left out. HARD PASS.
Also why not make Warrior, the beginner tank then since there is even less to manage, yet PLD can actually require some thought process to optimise using Atonement shift rotations, knowing when to squeeze out a Requiescat + Confiteor just before a boss jump, or using other methods to adjust your rotation to make it a gain, if you are so hard pressed to have a "tank for dummies" class. Personally, I highly disagree with your sentiments in the first place, I don't think it is mutually exclusive of each other, and that PLD is already a perfect example of it can work without need to sacrifice you for the other.
Hell a lot of new people to tanking only start once they get to DRK or GNB because they start 30 or 60 levels in, respectively. Honestly, your idea is flawed because those that level specifically to unlock DRK or GNB, probably won't necessarily pick either GLD or MRD as a starting class, and it shows in DF with some random tanks after 70+ levels in can't use cooldowns and still too chickenshit to pull more than one pack at a time, making PLD or WAR or any tank for braindead entry level in an already braindead entry level is an idiotic notion. Either people are gonna learn or they're just gonna have their weird entitlement and scream bloody murder because you dare give advice. Having a specific tank fill this role will only make one tank redundant at end game and defeat the purpose of making all jobs viable, while some who main a specific job will lash out in response.
Also why are you getting so hung up over one god damn cooldown less on PLD than the others also has a means to pool two on demands back to back, or time Intervention + Sheltron for double busters. PLD has PoA a second AOE mitigation with personal mitigation built in, time it right and you might lose an auto-attack at best, while mitigation only really matters in 8 man content, but even then you have 2 tanks, so you have two tanks worth of cooldowns. I genuinely have not run into an issue on PLD where I've thought "oh gee I wish I had another cooldown right now" in raids. Every tank has a ST support skill for their co-tank which also eases the burden on mitigation significantly. Dungeons are nothing but a face rolls, where you cycle cooldowns if you're out, well you have passive blocking, and things should be pretty much dead at that point anyways, oh and healers still have their excessively powerful and bloated toolkit.
What Paladin might miss ever so slightly in personal mitigation; it's balanced out by it's party mitigation and support.