If you are talking about the tax free lump sum then its hard to see any advantage to waiving your right to a tax free lump sum in any of the above situations.
If you waive it, then all you can do is take a taxable income with your pension fund at retirement.
If you are just talking about your pension fund in general then there are other options on leaving service such as transferring the current value to a new employers revenue approved fund or to a PRSA.
You should seek advice on this though from an independent financial advisor as there are a number of factors you dont mention like what type of pension scheme you are in now etc. that can affect any advice given.