Yes, you could take the max lump sum out of the AVC pot only and leave the main scheme pension undiluted.
BUT, you would have to make sure that the lump sum and undiluted pension when combined are within Revenue overall limits.
So you can extract the funds for the lump sum from the AVC pot and leave the pension portion of the main scheme and the pension portion of the AVC intact ?
I had always thought that you have to access benefits from both schemes together ?
Yes you have to access both at the same time. So if you are in a DB scheme (with the option to take part of your pension as a lump sum) and you also have an AVC pot; when you retire you could use the AVC pot to take your retirement lump sum (assuming it's big enough) and thus not reduce your main DB pension. That assumes the combined benefits (AVC +DB Pension) are within Revenue limits