It’s NE Bonsai standard stockNice looks like an Ed Clark tree
I would start with Shari and deadwood and finding the best angle.
I would definitely like to see this tree bigger, with a much more developed trunk caliper, with some dead wood. So, the best way to achieve more height would be to just let it grow?What do you want from this tree? Big, small, tiny? Thick trunk, thin? Dead wood or no dead wood? Small, young stock like this can be almost anything so you get to make the choices.
I would start putting in shari along the trunk. Start narrow and widen it every year or 2 as the tree thickens.
Looks like there's some wire scars mid trunk so you could follow those to give some spiral to the shari.
Letting a rear branch grow for a few years will add thickness to the lower trunk but @MichaelS is correct that all existing branches are rather high so thickening is likely to be uniform from there down. More height in the completed tree would overcome that problem but that depends on the answers to first questions.
It will take time to grow to that size. I would probably allow 10-20 years for that project. A larger pot or in ground will help speed up growth. Allowing some sacrifice branches to grow will help with both growth and taper in the trunk. Most of the current branches won't be part of any larger tree so no need to worry about any of them. Looks like most of the current branches come form very close together on the trunk. Do not allow all those to grow and thicken or you're likely to have bad reverse taper and pruning branches growing close together leaves big scars that can be hard to hide, even with shari.I would definitely like to see this tree bigger, with a much more developed trunk caliper, with some dead wood. So, the best way to achieve more height would be to just let it grow?
Thank you very much for this! it clarified some things for me. I didn’t think about planting in-ground, but I’m going to consider it.. the other option is a 3gal 10”x10” Rainscience fabric pot that I was going to experiment with.It will take time to grow to that size. I would probably allow 10-20 years for that project. A larger pot or in ground will help speed up growth. Allowing some sacrifice branches to grow will help with both growth and taper in the trunk. Most of the current branches won't be part of any larger tree so no need to worry about any of them. Looks like most of the current branches come form very close together on the trunk. Do not allow all those to grow and thicken or you're likely to have bad reverse taper and pruning branches growing close together leaves big scars that can be hard to hide, even with shari.
Keep wiring new growth each year to continue the bends and twists. Trees look very odd with bends down low then straight sections above. Even wire and bend sacrifice branches. Straight jins on twisted trunks look nearly as bad.