It's pointless to talk about regional client states in this globalized world, a country is either a satellite of a larger, more economically powerful country, or a financial haven of some type. In Malaysia's case, it is neither here or there. It is dwarfed by it's bullish neighbours, and it is competitively limited by it's own political constraints. Whether it can compete economically with Indonesia, Korea, Singapore, Thailand or the Phillipines in the near future, that remains somewhat uncertain. So for Malaysia in particular, it does make sense to have a very small airforce, to employed primarily for public display and the occassional maritime patrol duties it needs to keep up.
In that sense, and in view of the Mig and Sukhoi litany of contractual problems, I think the RMAF will lean heavily for the F/A 18F Super Hornet, at least 16 of those platforms to be precise. This is in keeping with the previous numbers of Mig 29s and would inevitably solve commonality issues. This would retain the total number of Heavy Class MRCAs in the Malaysian order of battle to 42 Aircraft, which is more than adequate, given Malaysia's limited ambitions.
The Hawks will off course be used for ground attack/bombing when necessary, and it is likely that the squadron of 13 types (unlucky for some) will be stationed in the Island of Labuan, off the Borneo Coast, to deter and patrol those areas, Malaysia contests as its own. Theoratically, the remaining 42 aircraft will be kept in Malaya.
So in a nutshell, i estimate that the RMAF can shed some 60-70 aircraft in it's current inventory (including the Migs and F5s) without losing it's original capabilities. Provided that the 16 Super Hornets are purchased.
As for regional deterrence, again this is unlikely. Malaysia has allies, and is allied to other countries, and has little or no territorial ambitions, apart from claiming Indonesian culture.