Low dose aromasin on a daily or eod basis will not hurt anyone. Neither would Arimidex, although aromasin is the much better choice. If someone is dumb enough to use a regular or high dose of Letro to manage e2 while on low dose HRT, it's their own fault if they crash their estrogen and shit gets out of whack.
An AI, when used RESPONSIBLY, by an INTELLIGENT individual, is perfectly safe and poses almost zero risk, and can help prevent SERIOUS side effects from high estrogen caused by high levels of androgens and aromatase activity in the body. The potential short and long term side effects from high e2 can be permanent(gyno) and dangerous(increased risk of cancer), and are far worse than the potential sides from low e2.