Tick-based indicators
Almost all indicators can be calculated on ticks (instead of bars).
Advantages – using Bid/Ask/Mid prices separately for calculations, faster signals.
The first thing that comes to mind is MACD, it will be like speed and acceleration. Next – oscillators. And levels like donchian / fibo.
Put this idea here so I don't forget, not sure if I can implement it now.
I think it depends on the strategy.
For me, the smallest unit would be 1-minute bar, regardless of the indicator timeframe. This would also work well for long-term backtests with 1-minute OHLC.
Another idea at this point: Indicator: today we have the current+last candle to choose from. Sometimes pre-last candles produce better results.
You can use custom bar with a Custom indy.