How to design a Power Amplifier
You're on the right track. I've only used the load line method for PAs with common source FETs, but the concept should be the same. It can be shown that the same load is valid for class A, class B, and others. Design for class A and mess with the bias later. Here are the basic steps...

Step 1: Select a transistor that can provide the desired output power

Step 2: Draw the load line using the max voltage and current of the transistor

Step 3: Calculate the necessary load from the load line

Step 4: While including the output parasitics of the transistor, add components to achieve the desired load