I disagree with the people who are saying it's impossible to combine FT work with providing a good standard of home education, and I would suggest that perhaps they don't have a very wide experience of HE. Certainly some teens do need a lot of support with their learning, particularly if they are working through a specific curriculum which doesn't match up well with their strengths.
But others don't, especially when they are doing what interests them rather than being made to do homework which isn't appropriate for them. Your child doesn't sound like one who needs a huge amount of support to engage with learning: "He will spend ages researching the Americsn war of independence or composing music on Sibelius software or writing drama scripts but gets overloaded by homework tasks." Home education often looks very different to school and does not typically involve the child spending hours a day working on an academic programme while his parent sits at his elbow.
More commonly, parents help kids track down the resources they need, and perhaps give them a little help if they are really stuck on something - or help them find someone else who can step in and explain. That isn't incompatible with working full-time.
I think your real challenge if you are thinking of HE is ensuring that your son doesn't get bored and lonely while you are out at work. Even adults who work from home often don't choose to spend all day every day at home but prefer to have some variety and a change of scene. If I were you, I'd be thinking about whether it is possible for your son to get out of the house doing something every day, whether he can connect with other people online and/or in person, whether a friend or relative can perhaps have lunch with him sometimes to see how he's getting on and ensure he isn't finding the day too long, whether he can get some exercise.
Do you live where there is decent public transport, and is your son able to use it to get out and about? What sorts of places might he go? If you don't have friends and relatives on hand, might you hire a childminder to spend some time with him? Maybe a local HE family could take him to activities?
Clearly you must be of the opinion that he can be left home alone safely or you wouldn't even be considering home education. He doesn't have to be supervised 24/7, but it might be nice for him to have someone on hand some of the time and not be alone for eight hours every weekday. Of course, if he settles into a more typical natural adolescent sleep pattern then he may not be awake for all of those eight hours anyway, which will make it easier.