Thought about it's philosophy?
What's there to think about? The Protheans were apparently aware of the Reapers long before they were actually coming. In light of that, all their actions make a great deal of sense. Their solution was wrong, but they had know way of knowing that prior to actually trying.
Omni-blades are garbage and what they did with omni-tools is garbage (forging an entire blade in a nano-second? ST replicators got nothing on this!).
Omnitools were always meant to be able to create simple parts for weapons and equipment on demand (it's why your **** never breaks down). You can reprocess entire mods into their component materials in seconds as of ME1. Casting a single, short blade, no complexity, and as far as we know not even mixing materials, and it's still hot from the process in (counting 'em) two or three seconds is well within the realm of possibility from the ME lore.
Besides, it's not like we can't magically generate flamethrowers with an omnitool that will burn better than white phosphor or napalm and burn through steel and ceramic composites even in a ****ing vacuum, or freeze people with cryo bullets, or a half dozen other things that are actually a ****ing whole lot more impossible than the omniblade.