Their tendency to ignore actual spellings of historical names in favor of modern variants is, as a linguist, one of the design decisions which upset me the most but which I don't complain about because it will change nothing. They're going to give characters in the game highly-anachronistic names or, more accurately, forms of those names so that they look more familiar to the modern eye. These were not modern people and should not have modernized forms of their names, but like the game itself being in classical Latin it's something I intend to either mod into the game myself or download a mod to fix, not something I expect from Paradox because they need to appeal to modern people to sell the game.
That said, I definitely favor the latinized versions of the Germanic names over the reconstructed ones both because the former are attested from primary sources and because runes are not a supported font in the game. Even the archaic-seeming characters used in the reconstructed names use a modified Latin alphabet which came along later, meaning that their names will not be written exactly as a literate Germanic tribesman would have written them in 450 AUC, and if we're going to use the Latin alphabet as a base then the names themselves may as well fit that.
