I can see why an indoor range would want to implement bullets without exposed lead. However, as pointed out, this will greatly impact loading tables and also ballistics charts. With the past several tens of decades where lead ballistics charts have been set in stone, plenty of alternative materials have been tested. The lack of HP availability in alternative bullet material, I can't see wide acceptance nor adoption as more than a specialty round for localities or ranges banning lead projectiles. For the military, maybe, but they are governed by different rules of engagement than civilians and even law enforcement.
If you practice exclusively with these light bullets, you won't be accustomed to the recoil impulse of the widely researched and tested, commonly available JHP defensive loadings. In my book, heavier is always better as I'm not only looking for deep penetration, but limited deviation of bullet travel as can happen to greater extremes with lighter projectiles.
I'm guessing the 5.56 bullets are somewhere around 40 gr, what is their terminal performance at 5-600 yd? What twist rates are the barrels? Given the current nature of military engagements, perhaps the long-range applications are being given little importance at this time?
I know OP probably can't answer then questions without breaching NDAs, but it bears mentioning. As stated earlier, we're just moving lead around, it's being neither created nor destroyed.
Have a nice day!