Mezonos, how can you regulate the legal aspects of it in America when the society is so opposed to plural marriage? The reason I brought up the social stigma is precisely that that is, and always has been, the greatest roadblock to plural marriage in America.
Just ask the Latter Day Saints (Mormons) and they will tell you. Brigham Young, who had 56 wives, which is probably too many for any man.
The Mormons in the west were applying for statehood for 40 years, but were ignored by Congress UNTIL they agreed to follow federal laws outlawing polygamy. Many legislators thought that the offer was insincere, and still didn’t support statehood.
I don’t see it happening in America, ever.
BTW, the 19th century Mormon polygamists did have a practice of marrying older women, widows and divorcees in order to provide for them. This would certainly help close the age gap and solve the shidduch problem.