If we're talking about long term investment than dollar cost averaging is about the same as lump sum on January 1st.

As for starting an ETF... Well minimal capital requirement is 100k, to launch it's probably 300k total investment. Then there is a lot of legal requirements and obligations. Whole process is at least 6 months

I guess it depends on what's your goal. Some brokerages let you create a bundle of stocks and share them publicly or privately. Which is sound more like what you want.