a good question. Maybe it is worth exploring if there are legal structures that can resolve the double taxation issue. For example, forming a corporation whether in Israel or in Us or in a 3rd party that will hold the profits. This is way beyond my expertise, I just hope that such methods are known to rich people and maybe should be shared with others also. It will a great thing both financially and hashkafically.
as to mutual funds, solution seems to be simple – just hold those investments that are tax-advantaged in your situation. There is no mitzva to hold all mutual funds in the world.