This post is still half-formed, but I'd prefer to put it out now and prompt some discussion rather then spend an eternity polishing it into whatever precise point I don't really have.
A sentiment I have seen expressed is that a character losing a limb or otherwise suffering debilitating injuries ruins play for them. While I do not take issue (or I like to think I don't and actively try as best I can not to :P ) with what someone else prefers, I do find there is a note of something ableist about the assumption that a character is ruined once their disabled. At the least it betrays a lack of creativity in playing them.
Add to this the pervasive notion in action orientated fiction, particularly fantasy, that the protagonists, 'heroes' even moreso, must be men of action (or woman of action still obeying the same archetypes). Characters who coordinate rather than use brute force are usually evil schemers, almost certainly so if they're men. This is part of the general fascistic anti-intellectualism in much of fantasy. A veneration of men of action and a vilification of the weak (and lookatthat, frequently, disabled) 'cowardly' schemers. I realize this is strong language, but it is a prevalent thread in our society and expresses itself in media intentionally or not, and the roots are, well, fascistic obsessions with strong, brave action orientated "heroes."
And among the men (and women) of action, note how rare is it for characters to suffer injuries which fundamentally change how they relate to the world. Or even for that matter to suffer injuries that inconvenience them for substantial periods of time. Power fantasy seems to forbid ever becoming incapacitated beyond a stagger and perhaps leaning upon a friends shoulder. Where are the scars? The amputations? The wounded being carried from the battlefield?
To that end, often when people seek to include disabled characters in fiction or roleplaying the power-fantasy approach of granting some power, or technological means of circumventing their disability is extremely common. Which is understandable! Its a power fantasy! But what is lost is nuance. As well it comes at the cost of exploring modes of Adventure that aren't bashing things and fighting (a general problem in much fantasy).
Furthermore! Lack of injury also cuts off a source of interaction with the world and ends up obscuring and diminishing people who occupy traditionally supporting social roles like healers.
Injury needn't remove characters from play, it simply requires re-framing how they interact with the world. Dismemberment and debilitating injuries are an opportunity for lateral growth and a chance to change up how you play your character. And debilitating injuries naturally fit into existing structures of play. Namely, hirelings!
The Hireling To Apprentice Pipeline
Hirelings and henchman are an immensely useful asset, and Apprentices are a natural evolution of the henchman. They form excellent back-up characters, moreso than random hirelings, as your already invested in them, and to add on top of that, they naturally provide structure for retirement and delegation, as apprentices can be delegates that players can play to carry out their characters wishes. In this you have extra-characters, more characterful than a more generic hireling, to act as extensions of the player.
For disabled player characters this is the natural route to interacting with the game world, the preexisting structure of henchlings offers the means to play a more coordinator type character.
Retiring characters can be unappealing, but becomes substantially more interesting with apprentices involved as there is now a character who has been developed already ready, with direct connection to the previous character and their legacy/impact upon the game world, all ready to be used as the new player character.
Furthermore, retired does not mean out of the world, simply incorporated into the background. In many ways its an investment, both retirement and apprentices serve to sink players into the social fabric of worlds. And when retirement is a natural life stage for all characters, it makes the prospect of characters who influence things not from the front of the show but the back more appealing.
Delegation & Deliberation
The concept of delegation is simple and stolen from this blogpost for the most part. Its a variation on the basic procedure of play. Instead of "describe situation" "players act" "describe result" it becomes "learn about situation through an intermediary" "order actions to be taken" "intermediary carries them out." It is a naturalistic extension of existing procedure to handle, well, delegating.
It is utilitous both in more broadly for handling expeditionary play, and more specifically for handling characters who work for intermediaries. In many ways it is simply a re-framing of an existing evolution in play adventure games can often go through.
Now the other option alongside delegation is to simply take directly control of henchlings and lackeys and see through their eyes. Which works well too, however I would suggest that delegation can center play on the coordinating character, keeping them the center of the players play.
The gist of all this is that the existing setup of typical adventure games are well suited for fitting disabled characters easily into the playstyle.
Now it is important to clarify that OSR adventure-gamey aren't inherently better at handling disability, rather they simply offer a different avenue of exploration.
I am not disabled. But I am queer, and the situation feels reminiscent of the matters of queerness in fictional worlds. Namely that a smoothed over "empowerment" style oft feels lacking of a certain meat and chewiness to it. There's criticism to be had with this, perhaps turning disability into some gameable element isn't an ideal route. Furthermore, I have focused upon physical disability here, and also, though unstated, on disability as result of injury. Mental disability is its own ballpark to be honest and I leave to be explored by others.
When it comes to technological compensation and "solutions" one must be careful, lest you fall into existing traps of eugenistic thinking that see's disability as something to be fixed. Prosthetics and other tools are just that, tools, that come with their own exsperiances and requirements to use.
In general it is valuable not to think in terms of costs or bonuses, as games tend to do, but think laterally in terms of how it changes a characters interaction with the world. The taxonomical math nerd urge to assign mechanical reward or mallus must be ignored.
Hirelings are a good solution in OSR gameplay context as its part of the existing playstyle, but there are implications to consider nonetheless; the relying upon others, or being a burden on others, not to mention the matter of wage relations for care which are a contentious and tricky subject. For the purposes of an OSR-y game where your playing skullduggerous dungeon delvers its less direct, but nonethelss still there.
See this excellent blogpost that elaborates on the matters here.