@backtrader "because when it calls your next (method with logic) the guarantee is that all buffers (data, indicators) have something. But you want some options only from a given point in time, breaking the entire system."
why should that be the case? NaN / missing values could be added into a series that spans 3 months across your 10 years worth of data. then you really may have multiple such data feeds that would be "active" / providing value just for a sub-set of your timeline. still, some built-in / helper functionality would be useful in "homogenizing" all these small time-span option series. would this be possible?