I like snake's swiftness mass myself, but you may want to instead utilize haste as it's longer lasting (Unless you need the actions right NOW).

If your goal is 'let him use a greatsword and a shield', try the spell compendium's 'shield bearer' spell. Transmutation and all, and means you can make it a tower shield to float around by your fighter buddy (Go buy a couple of them and shove them in your haversack / bag of holding).

I'd also suggest displacement as a helpful option, fly can help, and be sure to invisibility yourself to minimize your chance of personal harm (Greater invisibility can help the fighter). Most fighter types also like enlarge person for the damage bump.

Although it sounds like many of these things will become too effective for your DM and thus be banned.