Some class suggestions (if you make classes)
Paladin- Tanker
Beserker- Heavy melee damage dealer
Gunslinger- Heavy range damage dealer
Bomber- Heavy bomb damage dealer
Mage- Caster (if you ever make spells)
Summoner- Summons minion
If you pay 1000 crystal energy to someone you get the following advancement in the above class
Paladin> Heavens warrior- Really high health
Berserker>(2 choices) Dragon Knight- Really heavy damage with melee or Hell's warrior> Balanced damage and health
Gunslinger>(2 choices) Ranger- Accurate shots with guns or General> Really heavy damage with range
Bomber>Grenadier- Really heavy bomb damage
Mage>Arch Mage- High damage with spells and high healing power
Summoner>(Thinking of name)- Summons bigger, better and stronger minions
That's the list, reply some more ideas
maybe use the search function, to see what has been said about classes: but basically most people like the game when you can freely change from one thing to another, and many of the power ups you have listed can be found on Armour set bonuses
Paladin- vitasuit/ plate
Beserker- wolver, drake series
Gunslinger- this is already a series
Bomber- demo series
Mage- NO magic
Summoner- mechaknigts, but there is word/rumour of having more extensive pets.