That's what I wrote too, but I guess they don't want us to use "be" as a translation here. It's always a bit of a guess how much you should stick to the words really used, or try to make an english sentence - especially difficult if you are not native english ;)
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.
Is the pronunciation of "kanske" correct? Shouldn't it be "kanɧe" as in "sked" ("ɧed")?
Can you elaborate on the placement of "kanske". I thought it was supposed to go after the verb, but I think I've also noticed that "kanske" seems to have its own rules