I also feel this way. I'm not sure how to solve the problem. My money was invested in the first unit.
I had a 10%~ investment on it. I was very likely to get my ROI in the first month. Now I have roughly 1% share. I'm not likely to see my ROI until the very last unit is received and mining. Depending on how avalon ships, it could be less then a few weeks from the first to the last unit. But its likely going to be much longer.
I don't understand your concern.
If you had 7% of the 1st unit, and there were 7 more units added, you would have 1% of 7 units.
It is the same expected income and ROI.The trade off is that you will still have income if your machine is DOA.
You will also have less income if another machine is DOA.