Obviously this all depends on one’s opinion, but personally I think it’s important to do something you actually enjoy. As someone who has been forced due to illness to spend time around medical professionals, it clear when someone just loves the field or does not really want to be there. I recently had a CT scan, and there was a radiographer there - his enthusiasm and calm made me feel so much better, even though I had been incredibly anxious about it. So my point is, if you don’t love it, then how are you supposed to give confidence to your patients? You will come across patients who are in desperate, life-threatening situations, so making a positive impact in this way really matters imo. Also, working in hospitals can be highly stressful, so it’s important I think to make sure you want to take that on.
Secondly, as a fellow English literature lover (planning to do a degree and have an A* at A level), I couldn’t imagine doing something completely different.
That being said, doing an A level in English would take some financial commitment, so it’s important to be sure first.
I don’t have any experience of doing an A level in a year (it’s actually something I’m investigating for myself instead of resitting one of my subjects which was too low for my first choice), however I do have experience of being a private candidate (for my GCSEs). My understanding was that doing coursework is not possible as a private candidate (please double check though and don’t take my word for it as this might have changed). So you would have to do an A level course that doesn’t have coursework (which rules out AQA). Cambridge international qualifications don’t usually have coursework, so they are perfect for this, and that’s why I did their GCSEs. You normally just sit an extra paper or two instead of coursework.
The downside of this is that coursework is a good way to bank marks, and some people are particularly good at longer form writing. If this is you, do you have a good relation with your sixth form where you could maybe ask them to support your coursework, so that you could do an exam board that has coursework? This could also save you time, because if you are a private candidate you have to arrange a centre to sit the papers at, and it can be weird going into an unknown environment.
So basically it all comes down to what you want, what route would be best for you and the cheapest and easiest way to make that happen.
In terms of the actual A level, I don’t think it’s impossible to do in a year at all if you’re doing it alone (but keep in mind I’m not talking from experience, as I did mine in two years). I think the key thing would be to make sure that you’re still covering all the aspects (themes, characters, etc) of the text in a structured way like you would in class, so that you can write well on anything the exam board throws at you. But as you say you’re very motivated, this should be no problem. Plus the best part of being a private candidate is that you can choose the set texts yourself!!
Personally (again this is just my opinion) I think it shows real determination to a university that you would have taken an A level in a year through your own motivation.
Best wishes