Use disguisecraft and essentials. Essentials can let you do /nick for the name and disguisecraft for the custom skin.
The time required to fulfill your request compared to just you putting the two together are incomparable your request is not exactly "simple" sending false player data requires packet handling
When u are disguised as a person with disguise craft u don't talk with that persons name in chat. I think that's what he wants I suggest making a ticket to disguise craft
Use Essentials, DisguiseCraft, and Variable Triggers. Using VariableTriggers you can set /nick to set off disguisecraft without overriding the essentials nick command. Don't have the time to write out commands ATM, but I know it's possible.