Libra Officiantos

There are almost no wrong answers with Libra. He has an extremely universal statline, which can fit a huge variety of builds. Feel free to do whatever you feel is the best for him, because it will depend on personal preference and fodder options in the end. You could turn him into a more defensive supportive unit or you can turn him into an offensive/mixed phase unit thanks to the +spd IV....both will work with decent results, because he simply is a decent unit.

If you want an offensive threat then a speed-refined Wo gun with a classic desperation or wrath set will work well enough.