Ryan25,
This is doable. Many people have done it. Some did it because they indeed got married after the fact. Others did it, as it was one of the means to bring along a friend or a family. Other might have done for financial reasons.

Morality is thing you decide for yourself. I don't know you and I will never know unless you tell me. If they don't take 7-circles of jagge, then they are not married in your or my view. Its a 'fake' piece of paper between two people, with intention to circumvent the kanoon.

Is it legal. No. Is it moral, probably not. Not legal is almost always immoral too. sometimes legally done things are also immoral.
To your last question. I believe they have to stay 'married' for 2 years. I may be wrong. What issues that clause itself can bring into play? Lets see.
He will be responsible for your gf, legally and economically. He may be required to buy health insurance for her. He may be liable for her medical bills. Their credit may be tied together. You and your gf won't be able to get married 'legally'. She will have claim on his income and property, including Alimony. If you make her mother, in these two years, he may become the father and again buy medical coverage.

Your friend won't be able to get married until he divorce her. If he finds someone who says 'marry me', he will have to say no.

Can it be done? Yes
Will I do it? No
Should you do it? Your call