There are other interesting results from straight 3d6 in order. If you assume that every player adopts the character class most favored by the resulting stats, you should have a fairly even mix of starting characters from all available classes. That is, if you’re rolling up six OD&D characters where the only character options are fighting-men, clerics, and magic-users, it’s perfectly reasonable to arrive at a team that includes two fighting-men, two clerics, and two magic-users.
At least, that’s what you’d think, but it doesn’t really work out that way. Because the magic-user is the most likely to have the cash available, after buying starting equipment, to hire henchmen, a character whose highest stat is Charisma is likely to also be a magic-user, even if that character doesn’t have a high enough intelligence to qualify for the XP bonus.
I suspect this is an example of unintended consequences. Still, if you’re using a club or West Marches model for your campaign, you should also expect the number of magic-users to be weeded out fairly quickly. The lack of armour and low hit points is a deadly combination. The only class with a higher mortality rate would probably be the thief, if allowed, since the thief probably faces more save-or-die checks than any other class.
Which means that when you’re looking at 5th level PCs in the same group, you’re probably going to see lots of clerics and fighters, and only a smattering of magic-users who have managed to stay alive that long. That would make each magic-user of that level a very precious resource, and give the players with those characters a bit more clout in the group. “Yeah, well, if you guys really want to take on the trolls of the Greenskull Hills, you can do it without Frebble the Mysterious. Unless, maybe, you want to offer me a greater share of the treasure?”
And that, frankly, fits very well with the source material James Maliszewski’s been citing for the earliest editions of D&D. Wizards might be cranky, grasping, and difficult to work with, but they’re also too powerful to safely ignore. Throw in some mechanics that earn the magic-user XP for building magic items and you could end up with PC magic-users who rarely adventure, but are eager to hire other PCs to go on quests for the necessary ingredients to craft the potions, scrolls, and enchanted swords they sell to adventuring parties preparing to head out into the wilderness. I’d consider a class of PCs who were helping to create new adventures for the group like this a benefit to the game, and I’d probably say that they earn XP on a per-GP basis for any magical item they craft and sell to another PC.