Clearly, suspending involves letting paid staffers go, which affects cashflow that is reported eventually. I suppose Cruz can reactivate his campaign with only him and a few key staffers getting paid.
Ross Perot suspended and restarted his campaign, so I suppose it's possible. However, when Rubio suspended there were states that had rules for reallocating delegates to the remaining candidates. I don't think that reallocated delegates would be given back to a candidate who comes back. I don't recall any stories about states reallocating Cruz delegates the way they reported Alaska after Rubio suspended. Maybe Trump should look into whether states with reallocation rules followed through with the Cruz delegates.
-PJ