An early access section in Themeforest (similar to Steam) I think it would be a good idea.
Here’s some reason why
The best ideas require time to make, usually months or even years. Not everyone can make such a risk to quit
their full time job and to start working on a theme and not get any type of income during that time.
The most original ideas would be accepted and be part of early access until their official launch
This would allow developers to sell their work at a certain stage of development at a lower price, have income to fund their work, and get feedback by the community at the same time.
Risk of failure is lower, and authors would realise the product potential much earlier in development
Such a feature I think it will motivate talented authors and more unique products to become a reality.