I am not familiar with magus but was theory crafting a build and would love constructive criticism or if I have gotten anything wrong mechanically. This is for PFS with all attendant restrictions.
Human magus(kensai- whip)
S 7 d 16(18) c 12 i 16 w 12 cha 10
Bonus feat - weapon focus whip
Feats
1- weapon finesse
1- slashing grace
3- whip mastery
5- intensified spell
5(magus) - ?
7 - improved whip mastery
9-?
11?
The idea is to use the whips reach to extend touch spells and iajutsu and improved whip mastery to threaten with a 10 foot reach even while flat footed.