Unlock all the specializations from the start of the game

The correct answer is: they can.

I ran a Blood Mage/Battle Mage my first play through and I found out very quickly that a Battle Mage is really designed for tanking where a Blood Mage is designed to not take damage. If you have someone else to do the Tanking, then this actually works well as you become a semi-durable dps. If you're the tank, you quickly find out using heath as a resource is a bad idea.

• Unlocking Sakura: Play with Ryu, any level, and finish the game.
• Unlocking Dan: Play with Sakura, any level, and finish the game.
• Unlocking Rose: Play with M.Bison, any level, and finish the game.
• Unlocking Fei Long: Play with Abel, any level, and finish the game.
• Unlocking Gen: Play with Chun Li, any level, and finish the game.
• Unlocking Cammy: Play with C. Viper, any level, and finish the game.
• Unlocking Akuma: After unlocking Sakura, Dan, Rose, Fei Long, Gen and Cammy, finish the game in any level with any character you have already beaten the game, no continues, and a required amount of perfects(shown below). After beating Seth, you will fight Akuma. He must be beaten without using continues.
• Unlocking Gouken: After unlocking Akuma as shown above, beat the game using Akuma, then finish the game in any level with any character you have already beaten the game, no continues, no round loss, and a required number of perfects, super/ultra finishes and first attacks. After beating Seth, you will fight Gouken. He must be beaten without using continues.
• Unlocking Seth: Finish the game with all characters, including Akuma and Gouken.

Notes:

• Some of these conditions aren't necessary to face Akuma or Gouken after Seth, but if you don't match them, you will not unlock them for use.

• The required number of perfects, super/ultra finishes and first attacks change according to how many rounds are needed to win a match.

For 1 round matches:

1 perfect 3 super/ultra finishes 5 first attacks

For 2 round matches:

2 perfect 5 super/ultra finishes 10 first attacks

For 3 round matches:

3 perfect 7 super/ultra finishes 15 first attacks

For 4 round matches:

4 perfect 9 super/ultra finishes 20 first attacks