Japanese Maple Design Help

[Shibui]

How would you design it?

How I would design it and how others would design it should have little to do with your decisions. You need to decide what you want from this tree and work out how to achieve that.
All very well to decide to develop a world famous maple bonsai but need to be aware that will probably take 30-50 years. Maybe something to aspire to but most of us want a result much quicker.
The suggestions of chop and grow are all valid but the timeframes are years again.
Even layering to get roots close to the fork adds a year or 2 to the project.
If you aspire to a good bonsai and are willing to devote 5-10 years to the project you should follow one of the programs above.

Many beginners are more than happy to have a small tree with a rounded crown in a pot for their early bonsai. If that sounds like you at this stage you can simply prune all longer branches a little below your desired outline then keep trimming as shoots grow out beyond the size you have chosen. You can have a small tree in a pot within a couple of years. It us not likely to win any prestigious awards or shows but it will be your bonsai.

 

[rockm]

Love it when people suggest air layering to someone who is learning how to care for a tree in a container. It's unrealistic and simply delays the work on the rest of the tree.

Skip the air layer. It's a time-waster and will likely be unsuccessful, as it requires some pretty detailed work and correct timing to pull off successfully. It also takes months for the tree to accomplish. All that time you really can't do much else to the tree.

People will say air layering is simple and easy. It's not for someone just entering bonsai. Save it for a few years from now with better stock trees. There is no point in air layering a section of tree that doesn't have something worthwhile to use. You can get a long thin maple whip sapling for a couple of bucks if you look around and it won't cost you six months of time on the tree you're working on.