I'm not sure what is involved with adding lights but it seems like it would be easier to swap the drivers if they aren't pressed on. I will probably go with the all disc one in the case that boxpok wheels are not available as I don't want to end up with mixed, prototypical or not.
First you have assume Lionel will sell you drivers without the frame. Currently you have to buy the complete frame for the earlier J3s to get the drivers. Then assume they haven't used loctite on the screws. They did use Loctite on the TMCC drivers so you will want to buy new screws in case you have to drill some out. BTDT.
I would be surprised if Lionel omitted the Class LEDs even on the fronts without markers. It should be just a matter of swapping fronts and inserting the LEDs in the markers.
I actually have a front from 5444 that I would be willing to swap for a front without the class lights. Number plates and headlights are screwed on to the front so changing them out is no big deal.
Thats why I have suggested Lionel just include both styles of fronts with the engine and eliminated most of the discussion about this matter.