The Apollo capsules used hypergolics for the attitude control thrusters as well as the Service Module and Lunar Module engines. One of them was attached to Skylab for 3 months. Hypergolic propellants are toxic, corrosive, and generally nasty but we've been using them for decades. Their use is well known. There are satellites that have been in use for over 10 years whose propulsion system use hypergolic propellants. LH/LOX engines aren't a good choice for the CEV but they may still be usable on the lander, depending on how much boil off they have on the way to the moon. Hypergolic propellants may be a good way to go for the CEV.

Dropping the methane propellant engine may be a money saving move. There aren't any methane powered engines available so we'd have to spend a lot of money ($ millions) developing them. Given NASA's funding shortfalls, there may not be enough money to go around. Perhaps they could develop the methane engines later.

I have no objection to buying Russian engines if they're available and meet the performance requirements. The Russians build good engines (as seen on the RD-180 engine used for the Atlas V) and we'd save a lot of time and money using off-the-shelf engines where available. Some of it depends on the goals of the program. If the goal is to employ as many American (especially NASA) engineers, then develop new engines. If the goal is to go to the Moon and someday to Mars in the shortest time for the available funding, use off-the-shelf components whenever possible.