Mostly, focus on bringing them up to T4 first, attaining basic needed functions(theres a whole bunch of flaws with each combat style), before shooting for T3. The fighter as is, can be pushed to T4 with increased feat power, but T3 requires a dramatic leap in versatility, and ability to deal with non-combat challenges in some way at least.
Chargers suffer from low AC(you want every bit of charge range you can get, so heavier armors present a problem, you want every bit of damage, so non-animated shields are out), but with a few feats, enjoy a larger number of multipliers to damage than most other styles. Getting access to pounce somehow is the alternative to the massively multiplied attack. Additionally, they face the simple hazard of charging across the field and potentially across multiple reach zones, especially for large creatures that out-reach them.
Thats just one, an its an already effective style(mostly because unless they survive your hit or if they have friends your nuked AC is not really a concern). For more you could start another thread.
