I know this is one of the complaints against race as class, and I don't want to get to deeply into that here, but I would mention a couple of things I've observed over the years. First off, I've rarely (if ever) played or run in a classic D&D game where characters who started at 1st managed to run up against their level caps, even 14th for humans. Second, it's my belief that by the time characters reach those levels, a few more hit points or incrementally better THACO or another spell slot just isn't going to be that crucial. Hopefully PCs involved in the end game at that point are focussed more on the roleplay aspects of being commanders and high priests, etc.
Not to mention that when elves and dwarves hit their cap around 600K XP, the humans are all at about 11-13th anyway. Even if the demi-humans don't level up again and keep adventuring while the wizard is trying for another 400K or so, they'd still be seeing HUGE gains in terms of treasure (coin and magic) during that time.
End of tangent.
The Dwarf Lord follows a very similar model to the fighter's. He builds a stronghold and protects it. At 270K xp to reach 9th, the dwarf should have acquired enough loot for constructing at least along the Tarnskeep level of complexity. He attracts members of various clans to his territory. There is a lot of leeway given to the DM in how these clans are organized; be it by bloodlines, trades, homelands, or what have you. In keeping with the stereotype, dwarf holds are largely underground and often in mountains or hills. Dwarves will only hire or retain dwarf soldiers, but can hire other races as specialists, etc. One bit on X7 that intrigues me as plot-fodder says:
"There will be many different clans of dwarves, each gathered under the protection of a Dwarven Lord, but usually only members of the same clan will live together. Dwarven clans are generally friendly with each other and may join forces in times of need, such as when there is a war of natural disaster."
So the implication is that the clans don't necessarily get along. That's not to say that there is open warfare in the tunnels, but perhaps rivalries or petty feuds? Dwarves are known to hold grudges, after all.
In some worlds, they have a book full of them!
The "may join forces" line leaves the door open to the idea that they may not. A good leader would need to herd those bearded cats in times of crisis, and that could make for some fun diplomacy sessions.
Elves can become lords of their lands at 9th level, which takes them 400K XP to reach. This puts them later than everyone except, interestingly, Magic-Users. The assumed stereotype has these sylvan elves creating a base of operations in some spot of great nature beauty and seclusion. An interesting conceit to balance the cost to the PC is that the efforts of beautification (elaborate woodcarving, landscaping, statuary, or what-not) means that even of the elf-hold is not made of great stone blocks, it costs just as much. Like the dwarves, I find the default assumption of demi-humans retreating somewhat from human lands and being somewhat insular a definite, though not exclusive, trait of a BX setting. Like the dwarves, the elf lord attracts other elves to his hold, and only hire elven soldiers.
Elves have the interesting twist that they protect the creatures of the forest around them and, in turn, all the critters are friendly toward them. These animals can even bear messages to and from the elf lord. (!) Does this mean he can talk to these animals innately? Or does he give them a little scroll to carry a la "Game of Thrones" ravens? I say it's up to the DM, but personally, I'd let him speak to them and they can make themselves understood to the recipients via the elf lord's bond with them and his magical nature.
(I don't know why I went all Rankin-Bass on this post!)
What a wonderful plot device for low level PCs to be at a village and have a fox come out of the woods to deliver a warning from the local NPC elf lord about some imminent threat!
Speaking of magical natures, I should also mention that as a 10th level spell-caster, like the magic-user, the elf lord-wizard is theoretically capable of spell research and magic item creation. So in addition to his duties as a leader among his people he can also play mad wizard in his laboratory, adding to his arcane powers.