It's certainly legal. I'm assuming that you have left all the employments where the four pots were accumulated.
It makes sense as long as you make sure to "gross up" the amounts you withdraw as lump sums and are a 40% taxpayer. It makes even more sense if you will be a 20% taxpayer in retirement.
Current total pot = €493,000
Retire €265,000. Withdraw 25% or €66,250 in lump sums, tax-free.
Invest an additional €110,000 in AVCs. Net cost to you after 40% tax relief = €66,000. You spend your lump sums to replace this. I'm assuming that you spread the whole exercise over a period of years to stay within your 30% limit for tax relief (which will be 35% when you hit 55).
End result: you then have €199,000 (the other 75%) in an ARF + €228,000 in the DC scheme + €110,000 in AVCs = €537,000. The gain you make is the additional €44,000 in tax relief on the additional €110,000 put in.
Downsides ... from the year in which you turn 61 you must start making a withdrawal of 4% per year of the ARF. If you haven't retired by then, you'll be hit for high-rate tax and levies on this as it will be additional income over and above your salary.
When you retire the DC scheme, your maximum tax-free lump sum will be around €134,000 and anything above that will be taxed at 20%.