Its funny you should ask that.
First off - if you're working with just the normal HQ rules, with no advancement or anything...I'm really not
sure. Even the magical items that are offered throughout the game system and major expansions...that is,
the original game pack, KK, RoTWL, The Barbarian quest, and the Elf quest...it would be pretty hard for the four heroes
to do anything to a dragon (the dragon I've presented here). You'd have to offer some special magical items,
things that increase attacks, defenses, and body points.
NOW...if you were interested in using the rules I've presented here...that MIGHT be a different story. I made
four heroes last night - a human warrior (barbarian), a human wizard, an elf, and a dwarf (I made a human priest
too, but we'll leave him out for now). If you count in the magical items offered by the five game packs mentioned
above, and allow the training I've shown here - based on only the gold given to the heroes in the quest notes of
each game pack - then you could possibly make a set of heroes that could take on a single dragon and win, though
you might lose one or two by the end of the fight. I'll play it through tonight, if I have time, and let you know how it
comes out. If not tonight...definitely in the next day or two.
Now, a note on the training - to make the heroes that would be able to do this...using the rules I've presented here...
you would have to simply allow them to take the training as desired. You couldn't limit them based on the number of
days between each quest/quest pack. You would just have to assume they have the time for the training for it to
work.
That's one of the beautiful things about my rules system. You can actually make pretty powerful heroes, but the Players
will be limited on the amount of time allowed for training. They'll have to save their gold and bide their time until they
have the opportunity to do what they want to do.
All that aside - I'm glad you enjoyed the dragon presentation...I'm happy I could open up a possible avenue for you.

That's
all I can hope for.