When FICO 08 does get released, it will be awhile before lenders begin using it, from what I read.
My suggestion, work on your util and just leave the cards alone.
When you go for mortgage, if FICO 08 is in and the lender is using, and your scores are too low from not having the CCs, then(and only IF absolutely necessary) go joint.
My oldest account was opened nearly 7 years ago........it list on both EX and EQ, not TU.
EQ and EX also have many more accounts, and a extra collection. My longest account on EX and EQ is just 2 or 3 years old.
EQ also has no revolving reporting and has about 13+ more accounts than the other two.
You can see how the scores differ below.