The trick is, what you are proposing as a 'slave master' will be quite easily confused with a warlord on a warlitter - that is, an
actual character model rather than a fluff/interest/unit filler model. You will need to be very specific when setting up, letting your opponent know that 'this is not actually a character model.'
Other than that... why not?
I would rotate the speararms so that they are holding the spear horizontally overhead. Remove the spears, drill out the hands, and use dowels or brass rods to connect them in pairs. Then build the platform across two pairs, then put the guy with the whip on top.