I think deliberately making that type of change would be making things too complicated. Either you have 2-3 guys who can train in that role and are able to do it well, or you just don’t play that way IMO. Deliberately changing the structure mid-game would be asking for trouble.
It complicates things sure, but the complication is worth it to get the most out of your roster. To help simplify matters a little is why I said I'd start Williams so early game when it is generally less expansive he is on and use Billy for the rest.
To me playing Wilton before he is ready or moving Graham is more disruptive than having one ball playing lock and one non-ball playing lock. You definitely don't want to rotate them every 10 minutes but you don't want to do that anyway.
All things being equal you play Wilton over Williams for this role but at this stage they aren't equal, Williams is much more NRL competent. The difference is likely significant enough that you make it work with the different styles.
I doubt the difference between Billy and Willy is a 100% different game plan, unlikely we are using our lock to do a
huge amount of ball playing.
If you're playing prop (arguably the most 'simple' position in offence) for example you need to know the timing you can expect from two different halves, and the hooker (and bench hooker if there is one), and which other middles (because there is 2 or 3 on the bench too... and more in the squad) might pass to you if you run in support and which lines they like to run so you don't get in the way supporting. You learn how to play with your team.
In NRL you are training most days with these players if you can't figure out that Billy will likely play it on to you and Willy might but less likely then you're in trouble.
If Chad or Johnson look out and see Billy they should be able to call a play that everyone knows that involves him that would be marginally less effective with Willy.
Anyone ball playing should, wherever possible, let the players they intend to work with have a rough idea what they are planning anyway. If Billy is on and says 'hey mate I'll hit you back on the inside' you know what he wants from you, if he says nothing you support (and always be ready for the ball) but you assume there isn't anything specific happening.