Oi, what the heck does this mean? "[noun] ni dekiru"

[Cyborg Ninja]

その浮浪児は、いつか自分に子どもができたらゆりかごにできると思ったのです。

I understand the sentence above to mean "As for that street kid, he thought a cradle would do well if one day he would have children himself." But I don't understand why or what "ゆりかごにできる" means. Able to do cradley? Be fit or work well as a cradle? I don't know the grammar rule for this. What's weirder is he's using a slipper as a cradle, but that's another story.

[NileCat]

It is NOT another story.
The basic form is:
A を B に する
to turn A into B
to make A into B
to make A B
to use A as B
to regard A as B
to liken A to B
～にできる here is the potential of する. (be able to do)
In this case, 'A' (a slipper) has been omitted.