No one wants to spend much money at the conceptual stage, but you may have to, by farming out a basic loadflow study after some (admittedly, educated-guess) ‘hard’ numbers are assigned. Characteristics that may only be provided only by the serving utility are source-impedance parameters; else, what is the change in voltage at the supplier’s end of the line when loads are fired up?

Determine if it’s cheaper to reduce harmonics at the source {load} than to increase line-harmonic tolerance [id est, line losses resulting where harmonic effects are turned into heat.]

Contact an electrical PE familiar with utility-distribution practices and costs, for preliminary help in developing an RFP for line design