These are good options! However, they are all pretty much the hardest subjects at a level. Perhaps it would be best to only do 4, therefore you'll have free periods to revise and get the highest grades possible! I wanted to do 5 too, but I did 4 and really appreciate that free time, especially because I'm able to put more effort in.
Drop Further Maths, no need for 5 AS and since you're applying to Cambridge make sure you get the highest UMS possible in those 4 subjects. Being academically strong at GCSE means little when doing A Levels, different league altogether, imagine each of those subjects as the equivalent to 4 GCSEs, would you be comfortable doing 20 GCSEs?
Hey I started a levels this year. I do 3 subjects; chemistry, biology and geography. I wouldn't recommend doing 5 because you won't have a lot of free time to spend on your work. The most I would recommend is 4 but with the new changes to a levels you only actually have to start with 3 (that's what we are doing at my school).