I'm an old school purist. Moving lights have their uses and place.
Theatre is debatable in my opinion.
I would say your views are well out of date then. There may have been a time when movers were more basic and what you've described would make sense. But modern day movers have optics which are as good if not better than the
conventional equivalents; but this is combined with the ability to produce any colour (using
CMY mixing), occupy several different focusses in the same show, and produce a wide variety of creative effects.
Time is money. Theatres don't like being in rehearsal, they like being in show, because shows sell tickets and rehearsals don't. Movers can offer drastic time savings because they can easily be focussed whilst the
stage is use, different colours can be experimented with across 30 lanterns on a single
button press. It would take at least an hour using
gel frames and access equipment, and A/B'ing them all at once is practically impossible. And what if you knock a
conventional? You have to back and refocus. Knock a mover, and it will still go and find it's position as it did before.
Truck space is money. If you can get one mover to occupy 3 position focusses with 3 different colours, you could cut 9 conventionals. Think of what that is saving in terms of meat racks full of lanterns,
dimmer racks, cable trunks,
etc.
Labour is money. Techs focussing lights need to be paid. Movers being focussed by the
programmer do not. Constantly running up and down a ladder / scope /
etc introduces fatigue which can then present
safety issues, planning time for more crew,
etc etc. Movers being done at the programmers leisure do not have this issue.
As you can see, there are many financial perks to using movers before you consider the creative possibilities. They are a greater financial outlay to begin with but offer many avenues to reduce time, workload and ultimately cash.
I would never advocate a
theatre going completely one way or the other. Conventionals still have plenty of purpose and I use them all the time. But to even say that the value of movers in
theatre is "debatable" is not singing in tune with the realistic needs of the modern
theatre at all. They're an important piece of kit that theatres should definitely embrace.
My main doubt in this particular scenario, mind, is that 4 is just not a worthwhile
purchase IMO. You can't do enough with 4 movers to make them a worthwhile addition. I would say you would need to double or triple that before a designer can really incorporate them usefully. If you want 4 in use you should at least buy 5 - it's not unfair to expect to have one mover on the bench all the time. But more urgently some suggestion of what the OP wants to do with the movers is really needed. There are different sorts of movers, and no realistic recommendation can be made without that information. I mean recommending spots is fine but what if they want framing shutters? Then you will want a
profile. But if it's just for colour
wash, you'll want neither a spot or a
profile, but a
wash. Do you want
Tungsten or Arc source? What kind of lumens count?
CMY mixing (for me - it's essential in
theatre)?
Zoom?
Iris?
Frost? It goes on. There are a wide range of fixtures out there and not nearly all of them will do the job you are looking to fill. As Len said, don't try to buy something to later find a job for it.