Effect of NSAIDs, ACE inhibitors and ARB on kidneys 

Your idea is plausible theoretically. However all medications have side effects, some people might experience them, some might not. We weigh the benefits and harms before prescribing someone medications. ACE inhibitors might cause hypotension in a diabetic with a normal blood pressure. It may cause annoying side effects like a dry cough in certain populations. Research need to be done to justify the cost and risk of giving the medication for prophylaxis of kidney damage in diabetics without hypertension. I would say the better approach would be to advise dietary changes (low carb, low sugar) and exercise first to treat the underlying diabetes rather than adding more medications.

In line with your idea, the current recommendation is that diabetics with hypertension would benefit from a trial of an ACE-i as the first line drug because it helps with both the hypertension and gives some renal protection at the same time.

Also your proposed 'low dose' needs to be tested to see if it has any physiological effect on the body or any practical benefit. Too low of a dose and the medication might not actually do anything to the body at all and it becomes like homeopathy which isn't proven.