I think if the economy is bad enough that you need a lodger, it’ll be bad enough that people would need lodgings!
I can’t see the tax free allowance changing on rent-a-room, it never gets talked about as an option for cutting to save money.
Don’t forget that you can also take 25% of your private pension tax free in one lump sum. For small pensions, you can take the lot - it’s called “trivial sums” which makes me laugh as I think it’s up to £30K which is far from trivial! Obviously that’s not always a good idea. But it is a way of propping up a state pension short term, when you’re in your youngest pensionable years and possibly more active.
You mentioned raising £60K from downsizing. That cuts out the lodger option, but does give you 10 years worth of the extra £6K to you. Until you’re 77! And is thar just downsizing? Try to downarea instead - keep to a 2 bed, in a cheaper area. Pocket the cash and the regular income.
Basically: stop thinking of pension income as this one number from age 67, no possible change. You can use up “pots” (downsizing, tax free lump sum) sooner if you want to. Then coast along on those until (say) 77 and go for equity release to coast another 10 years.
You don’t need euthanasia as your backup plan. A lodger is a better option 😉
But if you really were ready to die, you can do that by suicide, regardless of government legislation. I doubt you’ll want to. You’ll be having a nice social and comfortable time with that lodger and your part time job!