How much do you trust the Collection class?

[DEXWERX]

So, if I understand correctly, you're proposing that there are two additional structures (one a hash table (small-ish array) and the other a complete sorted array of collection entries).

It seems you're off in the weeds... I didn't say anything like that. To implement an identically functioning Collection class, you wouldn't need any additional structures beyond VBCOLLECTIONITEM. It is however probably that the Collection Class uses an Array of Buckets. The Bucket could be an array of 2-3 VBCOLLECTIONITEM(s).