I also think some hard cuts are the way to go.
1. First I would work on the roots. Maple bonsai really should have good nebari and it is easier to do that at the start than to try to do a patch up job later when the top looks good.
2. Long internodes need to go. It will only ever sprout buds at nodes so you can't get new branches to grow between. If the trunk or branches are made from long internodes the branches will be too far apart. The best option is to cut them all off and grow those sections again (and sometimes again) to get all trunk and branches made from short internode sections. Difficult to do for newer growers but really necessary for best results long term IMHO.
3. The thick branch on the main trunk is thicker than the taller trunk itself so does not look right. One of them should go. Taking off the thicker one would be best as the thinner trunk then has taper. Grow a new, thinner side branch from the buds that will sprout after cutting the thick one.
4. Find a spot for the front view of the tree. Trunk should go a little toward the back at first but eventually come forward a bit at the top. You still need to grow the top of this tree so just worry about the first move away for now I think. It is not clear from the photo which way those trunks curve so hard to decide where the best view will be.
I actually prefer the natural Japanese maple shape for JM bonsai rather than the traditional informal upright with horizontal branches. Typical natural growth pattern for JM is several rising trunks that gradually spread out until the tips are almost horizontal and form the 'branch' planes.
This one I have shamelessly plucked form Vance Wood's blog is the style I am talking about. I believe it is grown by Walter Pall
You don't need to have as many trunks but note the way the main branches (almost trunks) first head upward then gradually divide and splay out so the tips make foliage pads.
You can grow your Sango kaku any shape you want. i just find that many traditional informal upright styled JM look contrived rather than graceful.