How does adding なる make this phrase more "natural"?


Recently, I wanted to express the sentence " _Maybe they'd make good pets._ "
in Japanese. I initially tried to say it as such:

> [多分]{たぶん}いいペットでしょうね！

I was then corrected by a native speaker, and he told me that it would sound
more _natural_ if I expressed it this way:

> [多分]{たぶん}いいペット **になる** でしょうね！

  
Now, what exactly does this add to the sentence? I believe that in this case,
なる is being used to mean " _to become_ " (It's hard to tell for sure since I
don't have a kanji for reference.) Was it added simply to make the expression
more idiomatic, or is there a more grammatical reason behind it?




Simply translate them carefully.

> 多分、いいペットでしょうね.  
>  'Probably, they are good pets'.
>
> 多分、いいペットになるでしょうね.  
>  'Probably, they will become good pets'.

Don't you think the second one is closer to the meaning you wanted?

If you want to emphasize it is an assumption, you can say

> いいペットになりそうですね.

