Still looking at the good and bad about leveling your skills to 100 then making them legenadry.

What are the pros and cons to doing this?

A few quistions I have about it.

First I went the Heavy Armor route but did not put any perks into the light armor side. I am at 100. So what happens now if I go Legendary? My armor skill starts back at level 15 correct? What then happens to the perks I already used and then to those I have not? Will I still be able to craft all the Same gear I can now? Or will I have to re level and put those perks in again to be able to craft the higher armors?

I would like to hear the good and the bad from both sides of doing this...

Thanks.