Hi Scott,
large xClass trees are not uncommon. If you are using an older Innovator version (11/early 12), you might not be able to use the amount of properties you want. The first version of the feature couldn´t deal with large amount of data. Newer version support around 4000 property elements. At least these was the number I heard some time ago.
How do you plan to display the xProperties? Inside the standard Form element? I wonder if this will become "easy-to-use" considering the amount of elements.
There are alternative concept to work with xProperties. Aras has customization to display the xProperties in a relationship and not inside a Form. If you have a good contact to Aras, ask if they can give you some tips from other customer projects. They definitely have customers who use a ridiculous insane amount of xProperties.
I don´t use a xProperties a lot yet, cause I basically always had the same question like you now.
Hope somebody else can contribute more to this discussion.
Angela
