Buying a lesser maximize rod at level 7...or any level, really, is flipping stupid.  It costs WAAAAAAAY too much!
Spending magical lineage and/or Wayang Spell...whatever traits on fireball is also stupid.  I love it, it's iconic.  But it's a HORRIBLE spell.
If you *were* going to go this route, for gods' sakes, at least combine Persistent and Dazing Spell instead of Empower and Maximize.  Same spell level adjustment.  Everyone has to beat 2 reflex saves or instantly lose be dazed for 3 rounds.  Of course, I'd use dazing and persistent on a dozen other spells before fireball...
EDIT: 7th level wealth is 23,500 gp.  Lesser Maximize rod is 14,000 gp, which is actually lower than I thought it'd be, but still over half your wealth and questionable if you'd be able to obtain so early.