I can see what you are saying about certain inherent powers, but it's a very fine line because as soon as you take them out of context, it becomes a free for all of unintended delegation.Inherit powers include those needed to carry out the enumerated powers. Such as you can't make laws without being able to compel people to give you the information you need to write them. And with the power of the purse, comes the responsibility to oversee that spending.
Take your mention of the power of the purse. The 18 delegated power mentions the governments responsibility to build and maintain roads, postal services, a military. For those things, money is needed, so they gave the house the power to raise revenue, so, while raising revenue is not technically part of the 18, it is in relation to them, in support of them.
So, yes, I guess you are right, that would be an inherent power, it's still limited in scope because it is in support of the 18.
What other inherent powers would you say they have?