It's necessary that either the concurrence of employees concerned or tripartite agreement if they are covered under a 'unionised' system when you think of any change in emoluments. While there is no need for any such pre-condition when you increase the emoluments on the contrary proper agreement is essential when the emoluments are reduced. I would suggest you should atleast issue individual letters to all concerned inviting their comments on your proposals, consider responses and act accordingly in order to avert complications in due course.
What you have to examine is, from the point of view of -
1) total emoluments, whether more or less, if less is not likely to be accepted- pl.ensure adherence to minimum wages as stipulated by the state govt.;
2) take home pay, if THP is more not likely to invite murmurs from concerned;
3) if reduction in basic wages/downward revision, which inter-alia likely to affect the contribution to EPF - under EPF act any revision in basic wages with a view to reduce the contribution to EPF is not permissible. May be, due to upward revision in basic wages deduction towards EPF is likely to be more resulting lower THP which the concerned employees would agitate;
4) keeping 'basic wages' at par but altering other allowances like HRA, conveyance, medical allw etc may be effected. If the policy on this will have the concurrence of employees/union, it may not pose problems to implement.