It's the easiest, sure. And masters of metagame should have no problem taking a cleric and being like, "Boom. Magic? He just has martial daily powers. Et Viola!."
The problem is that that's not how reskinning works. In order to reskin successfully you need to do something that is fully consistent with the rules as written. Reskinning works by treating the rules as an approximation of the gameworld (as they are) and seeing something else that fits exactly within the same scaffolding.
No one is saying that the Warlord needs (a) the ability to cast Turn Undead or (b) a Holy Symbol. In fact having either within the fiction is actively detrimental to the Warlord. (You can admittedly reskin a holy symbol as a battle banner to get round that little problem). And as for Martial Daily Powers, those words are meaningless within the fiction. What is meaningful is that sometimes when the chips are down our Warlord can pull out something stunning. That can't be hit by a Dispel Magic...
Reskinning works incredibly well in 4e because 4e rules are all about what you do rather than how you do it. If two things have the same outcome in 4e then they will have the same rules. Next (and most other editions of D&D) have deliberately separate rules for doing the same thing in different ways and tie in things like the source in a way 4e doesn't.
Reskinning a ranger as a fighter worked because there was literally nothing to the 4e PHB Ranger class other than the ability to use either a bow or two weapons really well, and training in either nature or dungeoneering. Absolutely none of which is incompatable with the fighter; the ranger was the single blandest class in 4e until the slayer turned up. The word "Ranger" has no game mechanical input so under the rules of reskinning it can be ignored - but to reskin properly
every single part of the actual mechanics which impact on the game world need to be matched.* The phrase "Pray for one hour each day to recover spells" does have a direct impact on the game world. It's something the character needs to do - and is entirely absent from 4e.
* The damage type keywords (fire, thunder, poison, et. al.) are a slightly odd case here because their impact on the game rules is minimal. This means that in theory you can not reskin a fire attack as a poison attack (or vise-versa) - to do what you want you are actively changing a part of the game rules. In practice most DMs will call it a reskin because the impact is pretty minor on the game mechanics although technically this is where we have left reskin territory and moved into house rules.
And I used to reskin in 3e - the Bard was exceptional for it. Two of my favourites were the Son of a Preacher Man - an evangelical preacher built using bard rules (he could even cast Cure Light Wounds as well as whip a mob up into a frenzy and give them morale bonusses with the power of his preaching) and the Charlatan - this bard was a street magician and conman who was lying through his teeth when he claimed to be able to cast spells but when it comes to low level enchantment or illusion spells if you're a mundane hypnotist and can convince someone you've enchanted them you might as well have done so. Combine that with smoke bombs, flamboyance, misdirection, and a fixed spell list designed for this style of play and there was nothing he did that he couldn't have done as a mundane conjurer in a world where people expected real magic. (Unfortunately I never found out whether he really was conning everyone or whether he was working actual magic through the power of belief and the main person he was conning was himself into believing his spells weren't magic). And the point about both the Son of a Preacher Man and the Charlatan was
nothing they ever did was a single milimeter outside the rules, and nothing they did used anything less than the full rules available to them. That is reskinning.