Think your missing the key point here. Romans were by and large money scrunging beaurocrats. Longswords were far expensive then any shortsword and took alot longer to make.

Quote Originally Posted by Companion
If longswords are so much inferior to shorswords in close combat then why use them? Esp. luxurious Royal Shield Bearers who could afford almost anything on the market? (albeit under the phalanx formation restrictions)
You hit on the exact reason here. Longswords are more expensive, thus the royal guards could afford them. It's not as though longswords couldnt thrust as easily as a shortsword could....

The reason the shortsword and scutum worked was that they were cost effective. Cost effective enough that if one legion was defeated, you could easily raise another with more shortswords and scutums. Personally I think the scutum is far more effective then the gladius hispanius ever was. Big, plywood shield, encases in leather and the edges protected by bronze.