The phrase "are merely on" is correct and usable in written English.
It can be used to indicate a state of being or existence in a specific context, often implying that something is not more than what is stated.
Example: "The results of the experiment are merely on the surface and do not reflect the underlying complexities."
Alternatives: "are simply on" or "are just on".
Many tourists who find themselves in Bangalore, India's third-largest city, are merely on their way to somewhere else: Goa, for instance, or Kerala.
With the obvious exception of their own sendoffs, a funeral is an event at which attendees are merely on the bill, as opposed to headlining.
Interloping journalists who are merely on the Web, rather than of the Web, are treated like Red Sox fans crashing the box seats at Yankee Stadium.
For organic-eating, right-living parents whose girls are merely on the fleshy side of average, "health" may also mask a discomfort with how a less-than-perfect daughter reflects on them.
While the bill's guide does mention "elected local representatives" (let alone the despised word "councillors"), they are merely on a long list of those designated as "best placed" to represent the new communities.
A run at the league mark, 33 straight wins by the Lakers in 1971-72, is unlikely, but the next five games could be what determines if Tracy McGrady, above, and the Rockets are merely on an amazing streak or if they are as dominant as they have seemed.
But he has disappeared and is now thought to be hiding in neighbouring Democratic Republic of Congo, although his FNL group says he is merely "on holiday".
When you watched a movie made for theaters on television, it was not television, it was merely "on" television.
Telling the girl, or not, is merely one step on a long and fairly muddy road.
Either way, it strains belief to suggest Mr. Quattrone is merely on a lucky streak.
My own kids were merely on the rambunctious side by comparison, if sometimes more greenly than at other times.
