Consider that is is common practice in lcs to lane swap. Consider that in some games, there might be a 2v1 top or mid and a 1v2 bot. You might have one player per lane and two junglers. You might have a support who continuously roams.
You might have the whole team walk up mid to begin with (maybe to invade jg) and then what, are they all configured mid? If not, how long would this system take to determine lanes and would it be constantly updating? That wouldn't be helpful after laning phase.
My point is that with the way different strategies are set up and the fact that riot doesn't technically enforce the meta, you're not guaranteed a top-mid-jg-supp-adc every game.
The configuration on any system like this would be severely flawed because anyone could be in any lane at any given time. If it doesn't decide roles immediately (which would be flawed due to jg invades), then it could have a delay. However, then say it configures when the jg is ganking? Is he then a "top laner" to the system because he was too when it decided?
I just see so many things that would make the system wonky, unorganized, and just not worth the time it would take to implement (even if it's a small time). While I agree that in an ideal world, a system like this would be nice, I don't think it would be accurate even 50% of the time if it was implemented.
TLDR; Too many situations/strategies/off-meta situations happen that would make the system flawed or less useful. Good idea, but not a likely or realistic one. Even if riot could somehow fix all the factors that would impede accuracy, the likelihood that they'd even implement this is low.