In the end it's still tax evasion, at least from a moral/ethical perspective. There is a reason that this topic is currently discussed in the european union in terms of closing loop holes for multi-national companies.
This will ALWAYS be cat-and-mouse games. Same as hackers, same as online movies, same as pirated satellite channels, as soon as one party comes with a "solution", the other one is already working on "breaking it". I would not hold my breath, for as long as there remains one single place on earth with lower tax system than the rest of world, there will be people charging heavy fees to come up with (legal) ways to circumvent whatever is put in place.
Btw Ireland has a universal tax rate which is low, for ANY company doing business there. It's not a "loophole" to domicile oneself in Ireland. Same goes for Cyprus. And both are EU members, and low tax rate is their way of attracting financial capital, investments and human capital.
Btw the lower the tax, the better for business growth, and general economic well being. Countries that try to tax to death find that businesses leave. I am sure that f USA had a universal 10% corporate income tax no US corporation would be even piling cash offshore, and would take all cash back home (and pay those huge dividends). Same goes for other countries.
Holland in France is abandoning the "millionaire" tax because it failed to produce any meaningful gains, and it actually caused many high-net-worth individuals to change their residence to Belgium and other lower-tax countries, thus actually having negative total effect on the tax revenue.
My personal opinion on tax issue is: require reasonable tax rate (preferably flat 10%, but not more than 15%) and businesses will gladly pay. there is a transaction cost associated with "finding loopholes" and creating all the structure and machinery to implement it, transact financially through the complicated international structure, etc. It needs more accountants, more internal checks, more subsidiaries, more paperwork, more oversight, more everything ... I am sure that if a company is given an option to pay simple 10 million tax on 100 million profit, or pay 3 million tax on 100 million profit but have 5-6 million of "overhead" and "transaction cost" associated, they would prefer to pay 10 million flat rather than 8 million through complicated structures which the bigger they get the more complicated they become and more incomprehensible they seem, even to the very corporate management. The only people that leave with smiling face are "consultants"...
Anyway, back to aviation ...