It is also very difficult to 'show' a combat system that is half-implemented. Calculating d20 vs. AC or 2d6+4 damage is easy. It only gets complicated when you have characters with conditional modifiers, buffs that change weapon size, etc. All of those choices that reflect on the character sheet (+stats, spell slots, etc) are being polled from the character in the same way they would when it comes time to do a combat calculation.
I'd say there is no need to "show" anything. Implementing the basic rules can be a decisive milestone. A prove you can do it, so to say. A test of your design.
And using the data in actual turn based combat might prove a total neck breaker. I.e. while doing the actual calculations, you might find out that your data design, which was pretty on char gen, is not flexible/generic/extensible enough.
I very interested in how you intend to tackle the combat design.
EDIT: showing stuff is fine, i mean - prove of concept is very important to avoid vaporware.