There are not too many provinces where you get good lvl 5 Regionals (most provinces only offer recruitable generals at lvl5) but there are plenty where lvl3/4 Regional unit types are very useful.

I use the Recruitment Viewer to work out what sort of Government to build when I conquor a province.
Not often a Type 4 but I remember an EB member saying that the progression from 3/4 up to 1/2 is the preferred method (gradual cultural integration) so I fairly often build up a type 3, then switch over to whichever of type 1/2 is available.

Once you get outside of your factions 'comfort zone', its all Regionals anyway.