As per Sec 27, yes second office is exempt from keeping sperate ca in practice as incharge, so we can keep income tax officer as incharge. But keep non-ca incharge of office, will lead to misconduct under S1 P1 Cl1. So end conclusion it is not allowed. Best thing to do is dont appoint incharge, everything will be fine, why appoint incharge when it is not required ? and get into trouble.