@AzizaWhenever I was on teams and we were planning experiments, whether we used a 'catalog of designs' approach (for example, a plain Jane 2**3 full factorial design) or an optimal design approach...whenever we had a proposed experimental design, we'd ask some questions like:
1. Will any of these combinations cause a known safety, or otherwise known or suspected hazardous condition that might 'break something' or worse yet, have a potential to cause personal injury or harm?
2. Given this design, are there other nuisance factors or experimental constraints we need to consider? If so perhaps we need to add some thinking around blocking (say, we've got to use 2 different suppliers for raw materials...and we want to guard against supplier to supplier variability) or, maybe we've got some 'hard to change' factors and it makes logistical sense to group the levels together (then a split plot approach...a form of blocking should be considered).
3. Do we need to consider response testing variability issues for the objects coming out of the experiment?
All these answers can influence the final design choice.