Any unethical practices should be avoided from a design standpoint. However, if a project does find itself in a situation like you have outlined the reality is they may take some of the actions you have mentioned. In contemplating taking these actions, the decision makers would most likely weigh what they stand to lose by remaining ethical against the likelihood and the consequences if their unethical behavior leads to a serious issue. Companies should probably have contingency planning and funding for when projects get delayed.