Yes, this is technically difficult.
10 points range bars is so called "Price based" period. When it is displayed in the chart, the time scale is no longer linear. You are asking for a possibility to display an indicator, calculated on the price based period, on the time based period.
Consider doing it the other way around. Why not displaying a time based period (use CUSTOMCANDLE indicator for this) on the price based period with an indicator calculated on it?
Attached is a sample of the SMA on 10 points range bars with CUSTOMCANDLE showing the 5 minutes candles.