I'm thinking with dense foliage the solar panel effect would be much less efficient if not much sunlight can get in. Also guessing you would end up with more of a bushy structure as growth would be spread amongst all of the small branches rather than being directed into a handful of branches which receive better access to sunlight and can be developed.
Also the risk of shaded out growth and interior die-back?
Both very valid points and real risks.
Sometimes bonsai growers focus on growth and thickening at all costs. The results can be catastrophic when we finally try to convert the frankentree into something attractive. I've very definitely moved away from growth at all costs and now focus on slightly longer tern quality results. In many cases I find the results are not actually much longer because grow at all cost growers fail to take into account the subsequent years it takes to heal large chops and develop taper and ramification.
Re-establishing foliage close to the trunk can be a slow and difficult process after interior shoots have died in favour of strong outer growth.
I've had much better results with junipers by using large sacrifice branches to strategically thicken trunks and branches while still keeping branches and apex under some control.
Also consider any bends and twists you might like in both trunk and branches now. Thicker juniper wood is notoriously hard to bend so establish bends now while the wood is still flexible.