Possible Spellblade Job Idea

[Deifact]

Now I have given this a lot of thought

Sorry to sound like an a-hole but your post doesn't make it look like you have. You've provided a very vague and wishy washy idea without any real specific ideas of mechanics at all, like why is it called a spellblade in the first place?

There have been Runefencer jobs in the past, which is perhaps what you were thinking of, but it would be hard to make them distinct from red mages in FFXIV.