Depends on what you mean by "plan related issues" Is the IC reviewing/consulting on plan design changes (settlor functions) or is the IC helping with gathering data/determining amount of benefits (administration expenses). Settlor functions-no plan assets. Administrative expenses--probably yes. And, as stated above, just because payment can be made for the services, it has to meet one of the PT exemptions (reasonable comp, etc..)
You need to be more specific on "plan related issues." See my comments above. If it is a function that the settlor normally engages in, such as making a plan amendment, determining plan design changes, then no. If it part of what is normally considered administrative expenses of the plan, then probably yes.
NO. NO. NO. NO. Don't even think about this.