conceptually your example is fine/good, but it's worth clarifying that the scheme you describe is insecure, as unpadded RSA fails to be IND-CPA secure. this is because Enc(m)Enc(m') = Enc(mm') is a predicate a passive observer can check, to gain information about Enc(m*m').

that being said, you can construct IND-CPA secure homomorphic encryption schemes from factoring-based assumptions iirc, so this isn't a fundamental obstacle.