Woody - warrant holders exercise and sell their shares at essentially the same moment - the warrant holders do not need to have a penny in their accounts. It is not common that retail warrant holders exercise and hold.
Some posts I read here that early calls for redemptions of NIOBW would be at $18, then warrants holders would have about $7 profits, if no cashless redemptions are offered.
As long as NB gets going, not much worries for warrants holders.