How wide is the building?

A few observations:

First, the purpose of a true ridge beam is to hang the rafters.
The purpose of a rafter seat is to support the rafters.

Thus, doing both is redundant.

If you WANT to use a dragon beam, use the seated rafter roof. If the building isn't too wide, you can just tie the rafter pairs with a collar beam located about the top third point. If it is too wide for this to work, you can add a raised kingpost. That is, keep the collar beam up there but add a kingpost between the rafters that pulls up on it. Or bring the kingpost all the way to the tie beam.

An effective way to get an overhang is to rearrange the whole assembly. Put the tie beams on top of the plate and extend them out past it maybe a foot. The primary rafters are seated into the tie. A secondary rafter is affixed to the primary ones at a slightly shallower angle and fastened to the end of the tie beam, extending below it a ways. This is a very good way of getting an overhang. Maybe I'll have to draw some pictures.

In this assembly, rather than the end wall beam joining level with the plate, they would extend past and work just like the other tie beams. This would not allow you to use a dragon.
If you want the dragon, you can lap the tie beams through the plate rather than passing them over with a cog. Then the end wall beams would sit level with the plate and you could place a dragon on them.

Also, where you have bolsters on top of your posts and a scarf joint above, there is no need for the lightning bolt scarf. You can use a much simpler scarf and peg it securely to the bolster block. The bolster itself serves much of the function of the complex form of the lightning bolt scarf, so you can save yourself some work there.

I am not sure I understand the problem B). If you extend the rafters, they will extend naturally in the planes they are already a part of. If the hip rafters lie in both planes, extended hip rafters will remain in both planes.
Swiss houses very often have hips set at a steeper angle than the main roof, framed by extended rafters shot out over the purlins. There is no problem here.

You can use a dragon, there are other ways to do it, but it all comes down to what you want to do. It's unnecessary sure, if you do it a different way. A tie beam is unnecessary if you build the roof a different way, too. It all boils down to whether or not your overall frame design makes it necessary.