The phrase "afterthought on" is correct and usable in written English.
It can be used when referring to a secondary consideration or reflection regarding a particular topic or issue.
Example: "The report included an afterthought on the potential impacts of climate change on local agriculture."
Alternatives: "reflection on" or "consideration of".
Mobile phone gaming is largely covered as an afterthought on existing gaming sites or is the focus of one or two business-focused blogs.
Two tormenting injuries, the more severe one in her lower back, have reduced Haworth to an afterthought on the global scene.
From a distance, brain autopsies seem an afterthought on life.
Something of an afterthought on the "Flashdance" soundtrack, but Summer never sounded looser or more giddy.
Golden State had almost always been an afterthought on the N.B.A. landscape.
Funny how rapidly story lines change, how what was in such strong demand on Monday becomes an afterthought on Sunday.
To sixteen chapters on the logic of categoricals, hypotheticals, terms and relations are added, almost as an afterthought, one on modal logic and one on the axiomatic method.
The coda contained the kind of soaring moral language — about human rights, American values, sacrifice, freedom — that Obama has generally avoided in his foreign-policy speeches, and it was so at odds with the uninflected explanatory quality of the rest of the speech that it seemed added on as an afterthought: hold on, this is war — I need to inspire people, too!
It's flat and cycle lanes are not just an afterthought tacked on by politicians with an eye on the green vote.
Bhasi's opening monologue reads like an afterthought tacked on to bring all the pieces together.
She added that social impact was part of Ms. Goldstein's D.N.A., and not an afterthought tacked on to her pitch just to secure funding.
