Well, driving around in a full fidelity tank would be cool but also get quicky very stale and probably boring/annoying. The AI is neither smart nor realistic. Very limited behaviour and heavily simplified. Maps aren't really made with ground units in mind (terrible pathfinding, getting stuck on bushes, questionable road layouts etc.). Graphics... Well, lots of graphical effects are missing. Interaction between units is also quite limited as of today.
You can do a standalone tank at it would function reasonably well. It's just when it comes to the ground war simulation, DCS is simply not anywhere near where it is to the air part (and even that one has big gaps in some areas).