I would like to use measures based off equity curve as a constituent of the train objective.

For that, I would like to use a min/max of a time series, linear reg slope, correlation, etc...elementary statistical functions..

Those happen to already be available in Zorro from TA_Lib.

TA_Lib inherently provides a list of functions, consuming standard arrays/pointers.

For some reason, you call them 'indicators' and only restricted their use to Zorro's 'series' objects (...but they actually work with std arrays in run(), but not in optimize())...

I really don't understand what's so 'indicatory' (and therefore 'strange' in your opinion) about linear regression or min/max of a series of values...