Crazy Ideas - How Far Am I Willing to Go?

  I am working on Tiny Kingdom (an adventure set in the garden of a mad arch-mage where the characters are just an inch tall) and updating The Book of Seaward (my book of house rules) and prepping a 2nd edition of Far Realms (my rues supplement for the OSR). I am also talking with the kids, playtesting Rolemaster Unified, rebooting a Champions campaign, starting a new business, and dealing with 4 family birthdays in just 15 days.
  So last night I was re-reading Hackmaster 5th because I have absolutely nothing else to do with my time and remember how much I like how they did the fighter/knight/paladin thing. Son #3 was getting some NPC classes (from my book Far Realms, an excellent stocking stuffer, if you'll forgive the hint) when we started talking about NPC improvement. One of his PCs has a hireling, a mercenary spearman, who has been to Skull Mountain 3 times and lived through it all. He and I agreed that this guy has done enough that he is no longer a 0-level merc, but a level 1 Man-at-Arms and can advance to at least level 2
  Son #1 joined in, asking about his 4th level Man-at-Arms, who is fairly tough and has been through the wringer. Son #1 asked,
  "Let's say he drank a potion of super-heroism, grabbed a +2 axe, and brought down, oh, a fire elemental. Could that be enough to transform him into a 4th level fighter? A 3rd level fighter?"
  We also spoke about the DCC 'funnel'; we've only glanced at borrowed rules and never played DCC, but the idea was interesting - can the schmoes of the NPC world become PC classes through Great Deeds?
  Then Son #2 came in with some of his work on Tiny Kingdom and his suggestions for some custom classes for the mice men and bumblebee knights and Son #4 asked if we should just break down and put a mini-retroclone section in front of Tiny Kingdom so it can stand alone; after all, with a bunch of new classes....
  But I said there are not just a lot of great retroclones already, the OD&D/AD&D books can be had, now, so if I am going to make a game, it will be different and new.

  20 minutes later we had this;

 It can be hard to see, but it is an advancement tree for the fighter classes. All start as Men-at-Arms and then you can either stay a Man-at-Arms or move on to Woodsman, Warrior, or Nobleman. Warriors can go on to be Weapons Masters; Woodsmen can be Weapon masters or Rangers; Noblemen can be Cavaliers; etc. It would be similar to the old Palladium RPG but you could move up, down, or sideways, as with hackmaster 5th. Men-at-Arms fight less well and have fewer HP, but a lot more mundane skills. Others trade skills for HP or fighting or special abilities. 

  The other 'big four' classes would have similar trees:

  Allowing players to mix, match, and customize their PCs.

  

  Again, this was back of the envelope stuff from last night - thoughts?