It would be complicated, but not a bad long term goal... Currently the Iberians are an amalgamation of the entire Iberian Peninsula. The Wonder and Temple are Tartessian... The rest of the architecture seems Celt-Iberian (Numantia). The units are a mix of Lusitanian, Iberian and Celt-Iberian... To date, nobody on the forum has been able to provide a full set of architecture- and unit-references for any one of those 4 distinct cultures (and there are other candidates as well, all minor players on the international stage). Separating them would make fleshing out each civ very difficult and make any semblance of historically accurate balancing nearly impossible from what I can tell.
Tartessian architecture could potentially be done (there's a few interesting archaeological sites). Units are impossible, I think. Lusitanian units lack diversity, architecture would be underwhelming, and they lack a navy. Celt-Iberians and Iberians are more doable, I think, but would also be the least distinct (Without those iconic Tartessian structures, and the addition of Celtic, Phoenician and Greek influences, they would be rendered a little generic looking, compared to the already existing civs). And then we haven't even mentioned siege, and language..