J4 has alot of utillity and can easily engage fights. Aoe %armorshred, aoe AS buff, aoe knockup on rather low cd, aoe slow, the arena from his ult. He has all the needed tools to keep his damage somewhat relevant without off items while enableing his team with utillity, which is what one expects from a tank.
For the 'otehr chamops', i'm not talking about darius or garen, more about Vi(lowish cd hard cc on Q, save lockdown for engage(vanguard) with ult, good synergie with iceborn for slows, or Xin, low cd knock up on Q, a decent slow on the dash, Aoe kockback+stun that can work for engage and disengage, even yasuo could work decent as tank, low cd aoe knockup, the aditional lockdown of the ult, his windwall, he offers a quite alot outside of just damage.
Also, it seems you mean 'physical damage' tanks rather than ad tanks. Physical damage is the damage type, ad is the scaleing. Those two are often related but frankly not the same.
I personaly would prefer ad-tanks, so champs that can do well with onyl 1 hybrid item like BC or Iceborn, but also have the option to go a bit more agressive in their builts.
Thats why i shoved the % hp scaleing on Sejus Q, it makes thematically more sense(well, atleast for me HP =body mass, so her chargeing in fullspeed scaleing off hp(mass) makes alot of sense). I also don't think it's that bad to add some more damage to it, it has alot counterplay(can be dodged/bodyblocked). It's not exactly uncommon to have a good bit of your damage on the mobillity/setup tool, Zac, Amumu, Mao, Vi, J4 all have their highest damage on their mobillity/cc skills.
To be an AD-tank, she'd need some decent **ad-**scaleings, and her W would be the most fitting place for that, but haveing both a total ad scaleing and hp scaleing on it would certainly be overkill.