The phrase "a mere starting" is correct and usable in written English.
It can be used to indicate that something is just the beginning or an initial point in a process or discussion.
Example: "This report is a mere starting point for our analysis, and further research will be necessary to draw any conclusions."
Alternatives: "just a beginning" or "only an initial step".
What's important about Yelp is not the star rating affixed to a restaurant — that's a mere starting point — but the site's sheer volume of reviews and the breadth of its reach.
While traditional commentators were still debating whether Teresa Heinz Kerry had gone too far with her "shove it" remark to the editorial page editor of The Pittsburgh Tribune-Review, the boisterous cyberrabble saw the comment as a mere starting point in arguments with the right.
View this as a mere starting point to build upon.
Sounds like a sad story, but the child's play was a mere starting point for a successful career in writing.
If Hume's remark is going to turn out to be a mere starting point, where in the name of all that's holy (really holy, genuinely holy) is the finishing line going to find us?
Similarly, while his Steve Jobs film is officially based on Walter Isaacson's biography, Sorkin used it as a mere starting point, and it took him a year to interview Jobs's colleagues, competitors and family.
This riotous culture worked to the firm's advantage in the days when it was a mere start-up, but became a hindrance once it had metamorphosed into a corporate giant locked in competition with the likes of Microsoft.More was at issue than dress codes.
Blockbuster Video had several opportunities to acquire Netflix when the streaming company was a mere start-up, but it didn't.
They consider natural proteins mere starting points for drug development, reasoning that a drug, which is treating an abnormal situation (ie, a disease), may thus need to produce an abnormal effect.
A recurring refrain among Mr. Malick's collaborators was the degree to which his scripts are mere starting points, extensively revised, even discarded, once shooting begins.
