Just another thought... XData can also be attached to Layers (and other Table objects). Attach your data to Layer "0" and it's pretty secure since you can't delete layer 0.
We started using this technique as soon as XData was introduced, before Dictionaries, LData, etc., and as long as you don't exceed the XData limit of 16K (I think), it works well. We store over 200 of our application specific "system" variables with this method.
Text files (.ini files) are used to store the initial settings, but if the variables need to change value from drawing to drawing, this system works.
We also use XData attached to entities and blocks. If XData had existed in the mid-80s, there would have no need for us to use attributes.