Could a HM-10 be powered by a LiPo with LDO?
No, you risk damaging the module if you run it from a fully powered LiPo cell. An LDO or other form of regulator is your only option when powering most things directly from  a higher-than-rated voltage source.

Perhaps if the voltage of the cell lowered enough you could power it directly, but it would keep drawing current from the cell all the way to 2V, which is far below the voltage you should discharge a LiPo to (I've seen various figures for maximum discharge, but they're all around 3 - 3.4v)