If he introduces a flat rate of tax, it'll be hellishly complex for defined benefit schemes anyway, but in particular for AFPS which will be fiendishly complex to administer. If he seeks to tax contributions at source, at marginal rate, an employer's pension contribution will have to be taxed at 20, 40 or 45% before a flat rate 25 or 30, or 33% subsidy (tbc, if any change at all) is added.
It will be complicated for everybody, but virtually impossible to administer in the case of public sector defined benefit schemes, and as for AFPS.. I can't even get my head around the notion of taxing a non contribution. In effect, some savers will be ‘fined’ for making pension contributions, before getting the flat rate benefit added. Too early.. coffee!
Either way, it won't be pretty - I'm thinking that if a serviceman of woman gets taxed on that which he contributes, in an instant, their rights will change. No more of the cosy amateurism that has defined how the military pension is implemented - and certainly an end to instances we had, when people were sacked days away from an IP.
He could just decide to get rid of tax free cash or reduce the amount you can take or reduce the annual allowance even further..