If in the example you quote, the Final Salary is €100,000 (so 50% Pension plus 150% lump sum), the answer is NO
If however this is a Post 1995 (Inregrated Scheme) then the Pension of €50,000 would be inclusive of the State Pension (Scheme Pension of c€37,000 + State Pension of c€13,000). So technically, you could invest AVCs to increase the €37,000 scheme pension up to €50,000.
But if the €150,000 represents 150% of Final Salary, then you cannot use AVCs to increase that to €200,000.
The Revenue lump sum limit is 150% of Final Salary. The first €200,000 of any lump sum is tax free, but you would need to have a Final Salary of c€133,000 to be able to take €200,000 as a lump sum.