I haven't been able to find a schematic that I can actually read, but it looks the bulbs are being powered by a DC source. Is one of the GI strings rectified somewhere?
As for the GI OCD fuses, they're very conservative values (2A SB) for F2 - F6. While I haven't specifically tested for higher current, you could increase the fuse value to support incandescents in the helmet. Just make sure to keep an eye on the MOSFET to make sure it isn't getting too hot. It's rated for 26A, but there's no heat sink on it, so it will not be able to run at the full rated 26A. Also, be aware of how much current you're running through the connectors. It's no more current than the game was originally running, but we've all seen burned up GI connectors, right? The fuse holders are rated for 6.3A, so don't go higher than that.