Cholesterol ratio

I have seen many differing opinions on this forum regarding cholesterol levels and even the british heart foundation seems to change its mind about acceptable levels in CAD patients roughly every two years. I assume this is due to research revealing more of the chemistry behind cholesterol. I have read reports where it is claimed too low a cholesterol level can significantly increase cancer risk. I have read that low cholesterol levels can affect the functionality of the brain.
I am wondering if the level of cholesterol is so important compared to the ratio of lipid types. For example, if you have very high LDL and a ratio of just 0.2 HDL compared to LDL then surely this is likely to produce a problem.
If you have high LDL but have 3 or 4 HDL lipids per LDL, is this a serious issue? If HDL is the cleaning mechanism to keep LDL in check maybe this is the key rather than the overal levels?
Is it not possible to harvest HDL lipids and inject them into a CAD patient on a monthly or three monthly basis? rather than using statins and other medication to try and alter the levels.