I could agree with the mechanics of
msu2001la but I wouldn't put a lot of money towards the bike. It is rare that a frame is special and they just put whatever low initial cost gruppo on it. I would just save the money and get the bike with 105 on it already you will likely get a much better bike and in the end save some money to a point. Yes a new bike is more expensive but buying a single groupset vs. any bike brand buying 100,000 groupsets is a more expensive proposition.
Ride this bike figure out what you like and don't like and then try some bikes that seem like they have what you want and save up for them or buy them and have this one as a back up or a rainy day bike or beater or something. N+1 is scientifically proven to make sure you have bikes.