It's not wrong and I assume it's accepted by now, unless it's considered too much of a construction change. But the expression det kommer en/ett ... is idiomatic in Swedish, and really sounds better to native ears. A little like "there's a ... coming" in English.
But we are not learning english! It is important to understand the swedish and use it right. English is not important! I am a german native speaker and in german it is almost the same expresion like in swedish. As a result, I can translate it perfect into german, but many times the english translation is total different, sometimes also by using total different words, translating for example går = possible. It is very confusing.
English is very important. We literally have tens of thousands of users taking the course to learn Swedish while improving their English. If we have to sacrifice some English idiomatics to better teach Swedish, we will do so - but we won't intentionally accept incorrect English.