I think the best way to make a fighting game deep is not just to have a bunch of options for your characters to do, but to make the value of succeeding with them fuzzy and hard to know in real time. This feeds player creativity and exciting "I've never seen that before" moments.

UNI: What exactly is the value of winning vorpal in this matchup and situation? Should I lose vorpal but get damage and position? If I win vorpal will I die anyway?
KI: What is the value of this meter? Use it offensively (which shadow? when?) or defensively (reversal? S.Counter?)

If, while analyzing video of a match, you have to pause the footage and think "was that the right decision? I don't know...", I think your game will be deep. Also note, not every decision must be like this (DPs will have immediate feedback on whether it was a good idea or not).

I think you can make a game with "lots of options" and have it not be especially interesting if they all have obvious risk/reward. You'll end up with "by the numbers" play instead of moments of unexpected creativity (and mistakes!) or varying opinions on what's strong and weak.