If there's a good chance of getting to level 15, definitely plan to get spell perfection. Get quickened spell. Strongly consider dazing spell. With those traits and spell perfection you can get off quickened dazing fireballs. If your buddy doesn't like dazing but just wants the fireballs to do damage, get intensify, empower and possibly maximize.
(Greater) spell focus is helpful as well for the saves, and again awesome with spell perfection. Piercing spell and selective spell are possibly worthwhile as well. For a pure blaster I'd say get the metamagic rods instead, but if you also want to wield a weapon that's more complicated.
As for combat feats, power attack is a no-brainer, beyond that nothing is really required, but if your buddy fancies heavy armor and a good weapon proficiency, definitely get those. I'd probably put most of the feats towards casting, but then put the ability scores and equipment more towards melee, as I think that's the best resource allocation if you want to do both.
So for an ability score array, maybe something like:
str 17, dex 12, con 14, int 10, wis 8+2, cha 15+2
Then put all level increases into str. If you make it to level 16, put that increase in cha.
And for feats, maybe something like:
1. heavy armor and good weapon proficiency
3. power attack
5. spell focus: evocation
7. empower spell
9. intensify spell
11. piercing spell
13. quicken spell
15. spell perfection
edit: Looking at that again, if you plan to apply multiple metamagic feats to a single spell as a spontaneous caster, you really need the spontaneous metafocus feat (or casting your spell will take longer than a full round). As a hybrid caster/melee fighter you really want to cast your spells as standard actions anyway so you can position yourself in the same round as casting a spell (or turning into a fire elemental). Thus, the one feat you really, really want and that I missed so far is spontaneous metafocus.
