Yeah, it's enormous and I can definitely see why that would be somewhat problematic when it comes to playability with 16 people. I think the reason I think it could be done is because of experiences I've had with the Battlefield franchise, particularly 1942. I know Battlefield has more players per match, but I think the play area is considerably larger than Sandbox in most if not every single situation and combat flows fairly well.
I think if you put a ton of vehicles on the map, made their respawn timers significantly shorter, start with battle rifles and have a focus on certain heavy and ranged weapons with flag and bomb gametypes, it might work well if its Forge-work integration is spread out. You would really have to focus on a larger volume of smaller and simplistic structures than the typical map which seems to include half a dozen massive or at least complex structures.
For example, a segment of the map could be a "forest area" where each tree represents maybe one or two pieces of geometry and takes probably a LOE total of 3-5 minutes, but the clustering formation of 25-35+ objects together creates and interesting playspace. Or maybe the map has two bases and a large collection of bunkers, depots, waystations with a slew of vehicles and spawn points at each -- all networked by teleporters. I think the biggest problem would be the amount of time it would take to flesh it out.