Interesting question. Why change tone?
English is called a stress-timed language. In English, we often shift the stress to change from verb to noun as in:
v. produce, n. produce, v. refuse, n. refuse
I wonder if this is also generally true for Chinese? It is worth looking into.
"My understanding for the pronunciation of 將 is 4th tone for verb " you may be a little confused there.
jiāng has a lot of possibilities. Here are some.
jiàng does not have so many, but, for simple cases, it is nominal in nature.
This link has so many uses for 将 you could get dizzy! There is no clear distinction verb/noun -- jiāng/jiàng
btw is Vibius Vibidius Zosimus really your name?