In Parts 1 & 2, I've proposed a cautionary note on NOT feminizing God the Father, but I haven't necessary enumerated the actual dangers in doing so, other than an implicit danger of displeasing Him through mischaracterization. Indeed, a reply to Part 2 suggests that the Holy See doesn't mind the title of "Mother" for God.
The foremost reason that comes to my mind is the dilution of what "Father" really means, not to God Himself of course, but rather to us humans as we look to God for guidance. Without the explicit Holy example of "Father" as creator, provided, protector, and compassionate forgiver, we human men are subtly (or not so subtly) coaxed into giving up those roles in our daily lives. It's sad but apparently true that without constant focus on our "manly" responsibilities, we face the real prospect of leaving our manhood at the proverbial door, or more properly at the boat dock, or the couch, or the stadium, or the internet porn site.
We see and live this every day, the temptation to ignore our "manly" duties and thus leave a void in support, instruction and ultimately love for our families. Worse yet, the void in many cases is filled by women. This fear isn't misogynistic, it's social justice. Our families, particularly our wives, deserve to have men do their part. Take it from my personal witness: the disappointment and disarray when I wasn't attending Mass with my wife and children, and by contrast the visible relief and satisfaction in the whole family, not to mention the improved attitude and behavior of the kids, when I started attending Mass as a Catholic father should. Women will step up and cover our consciously-chosen deficiencies, but why should they have to? Why would they want to?
Man up, men!