I couldn't find a thread for this, as it covers a few areas. Looking at a flight next year from TPA-LGW. There is a nonstop AA flight, operated by BA, that is available for AA points.
Awards available: Main (30K+$237USD), Premium Economy (40K+$482USD), and Business (57.5K+732USD)
Cash prices are $470USD, $1143USD, and $2353USD.

I am wondering what the options are to pay cash for the ticket, and upgrade vs using a partner award.

Question for clarification:
1) I believe EXP complimentary upgrades are not an option?
2) If I book through BA (zero BA status, but OW Emerald), do I have any upgrade options? I am guessing no, but I've never booked through BA. (The only reason I would do this is to earn more AA points, or alternately Avios points which may be my next "currency").
3) I located a "SWU strategy" thread, which I need to read to determine if this is an appropriate avenue. If there is some way I could guarantee confirmation on booking, this would be great... unless I need to purchase the PE ticket to get to Business, which may be the case??
4) If booked through AA, I believe there is a points+cash upgrade option, which I call in to customer service for? Is this generally a good idea? Are these just one class upgrades?
5) I believe I can also wait for the app to offer an upgrade for cash price, which could be hit or miss. Are these just one-class upgrades?

What it boils down to is getting into business class the most economical way I can find. This may end up just redeeming a partner award, and paying the $732 fee, but still looking for experienced recommendations on if there is a better way.