Designation - Employee Resignation

Hi,
Whereas I appreciate that person is new, designating him as senior executive seems a bit exaggeration/over-designating him, however, suffixing Operations may be OK.
Regads
S.K.Johri

Project Coordinator can be an appropriate designation. Since he is coordinating for different projects to different stakeholders.

You may consider the designation as 'Executive - Business Relations' which could adequately cover the job responsibilities assigned to the individual. Just inform the individual verbally first, see the reactions & formalize accordingly.
In small organizations, HR has a unique task of creating designations & new job descriptions. Enjoy the learning offered by such opportunities. There is nothing known as 'standard designations/ job titles'.

Sujata
When you are not clear what designation to give, just stock to the simplest one.
There is no need to complicate life and titles by making it long and specific.
If he is a fresher , give : executive or junior officer
If mid level, : Jr. manager, Asst Manager
Upper level : Manager, sr..manager
You can write the department if you want, or just keep it blank ! Nothing wrong with it