Can the nib be replaced with a Lamy nib?
Sounds like a fun experiment... I've had a few around the $2-4 range that have really surprised me positively. BTW... that does look like a #5 nib on that one... and almost all chinese pens with this type of nib were removeable/friction fit (up until now..). I have a Baoer 516 that I refitted with a Franklin Christoph medium stub. Works pretty good.
Have fun experimenting!!