I agree that reasonable adjustments should be made but some of these are not reasonable and are frankly crazy! Lets run through:
Redeploying someone to a different role if their original job can’t be adjusted Absolutely this is very reasonable and should be the absolute base level
Promoting or transferring them to a better-suited role, even if that role comes with higher pay or more opportunities, if it helps remove a barrier Absolutely not, promotion should be done on the basis of who is the best fit for the role. Are you honestly saying that a company should promote someone with a disability because it will make their life easier rather than promote the person who is the best at their job and would be the best in the promoted role? Forcing companies to promote the wrong person is a horrendous idea!
Reassigning certain duties or tasks, even if this means the person is doing less than others While I can see the reasoning behind this again its just not a practical option, people are paid a salary to do a certain level of work, if someone is unable to perform at that level for whatever reason they should not be paid the same as other people. What happens when one able colleague is fired for poor performance and a disabled colleague is kept on despite doing less work?
Reducing workload or output targets, such as call volumes or deadlines See above
Allowing home working, even if the original role was office-based Absolutely should be able to do this.
Offering a less senior or less stressful position but keeping the original pay, if it prevents the person from being pushed out entirely Again this is an awful idea, you cant pay someone extra money for a lower job no matter why they need it.
Ultimately if your suggestions were to be implemented I can assure you that they would result in companies never hiring anyone who may have a disability again, why would you knowingly hire someone who is legally allowed to perform at a level you would fire other staff for?
If you then tried to put in quotas for companies needing to have a certain % of staff with extra needs it would result in them only being hired into the most junior positions. Why would you hire a £100k a year Software Engineer who is only performing at 70% of the level you expect (costing you £30k a year) when you could hire a £25k a year cleaner who performs at 70% (costing you £7500 a year)