This is the haste from the d20 modern SRD
Haste
Transmutation
Level: Arcane 3; Components: V, S, M; Casting Time: Attack action; Range: Close (25 ft. + 5 ft./2 levels); Target: One creature; Duration: 1 round/level; Saving Throw: Fortitude negates (harmless); Spell Resistance: Yes (harmless)
The transmuted creature moves and acts more quickly than normal. This extra speed has several effects.
When making a full attack action, the subject may make one extra attack with any weapon he or she is holding. The attack is made using the character’s full base attack bonus, plus any modifiers appropriate to the situation. (This benefit does not actually grant an extra action, so a character can’t use it to cast a second spell or otherwise take an extra action in the round.)
The subject gains a +2 dodge bonus to Defense. Any condition that makes the subject lose his or her Dexterity bonus to Defense (if any) also makes the subject lose dodge bonuses.
All of the subject’s modes of movement (including normal movement, burrow, climb, fly, and swim) increase by 30 feet (to a maximum of double the subject’s normal speed).
Haste dispels and counters slow.
OK I really do not like this spell as is, but it seems to fill a niche in d20modern.
Now look at some spells from the d20 system SRD
Expeditious Retreat
Transmutation
Level: Brd 1, Sor/Wiz 1, Travel 1
Components: V, S
Casting Time: 1 action
Range: Personal
Target: The character
Duration: 1 minute/level (D)
The character's speed and maximum jumping distances both double. These benefits count as enhancement bonuses.
Haste
Transmutation
Level: Brd 3, Sor/Wiz 3
Components: V, S, M
Casting Time: 1 action
Range: Close (25 ft. + 5 ft./2 levels)
Target: One creature
Duration: 1 round/level
Saving Throw: Fortitude negates (harmless)
Spell Resistance: Yes (harmless)
The transmuted creature moves and acts more quickly than normal. This extra speed has several effects.
On its turn, the subject may take an extra partial action, either before or after its regular action.
The subject gains a +4 haste bonus to AC. The subject loses this bonus whenever it would lose a dodge bonus.
The subject can jump one and a half times as far as normal. This increase counts as an enhancement bonus.
Haste dispels and counters slow.
Well as long as
Expeditious Retreat exists in Dungeons & Dragons I see no reason to change
Haste to the version that exist in the d20 modern SRD, it is really a too big trade-off for a 3rd level spell in Dungeons & Dragons where you have
Expeditious Retreat as a first level spell (change is really just +2 to AC for two extra spell levels). In d20 Modern however
Expeditious Retreat doen't exist and the spell fills a purpose there.
A spell on an arcane casters list should primarily affect the casters ability to survive and deal damage in combat, while its secondary effects should prove effective on allies/other classes. For buffing spells we have the Divine Casters, their spells is their to aid/help others. As in Dungeons & Dragons I see nothing wrong with haste, an arcane spellcaster per the core rules/SRD benefits more from haste then the other classes which in my book is just fine. Still the AC haste bonus on can argue about, but I find the spell just right.
If haste was changed to the d20 modern haste and if Expeditious Retreat still will be in the book the spell goes from a no-brainer to a no-way which is not a way to revise a spell in my book. If you need to change the spell just remove the haste bonus to AC, otherwise I feel the spell works fine.
And for having an addtional action, well it is not how many actions you have it is how you use them according to the situation (sure a smack-down thread about what you can do always uses haste, but remember that is under optimal conditions). Remember optimal conditions doesn't happen all the time, and for spellcasters that needs to memorize haste, you have to know that there is a great chance of a powerful encounter to actually validating a memorization of it.
For Sorcerers it is a bit more powerful so maybe you should buff it to 4th level on the Sorcerers list, but in my opinion it is a 3rd leve wizard spell. If one should change it then remove the haste bonus to AC.
My 2 ören