Should you move your back leg first or front leg first?
The half step XingYi Beng Chuan is famous but the footwork may have some risk involved.
http://www.youtube.com/watch?v=pvAfiEBPegA
When you step in with your leading leg, your opponent can:
- kick your chest, belly, knee,
- sweep your leading leg,
- scoop your leading leg,
- crack your punching elbow,
IMO, to step in with your leading leg first is just like to throw a cross without a jab first, you may over commit and expose yourself when the timing is not quite right. It may be better to move your back leg behind your front leg first. This way since the distance between you and your opponent hasn't change, you can withdraw your back leg if needed. Also when you move your back leg first to make your back leg to touch your front leg, you can advance and withdraw whatever that you like. When you move your leading leg first, your stance may be too wide to recover from any mistake.
What's your opinion on this kind of footwork?
Every move involves some risk
If you want to avoid risk, avoid combat. There is no such thing as a risk-free technique.
This reminds me of your The risk of the TCMA hammer fist thread.