I've literally spent the last hour thinking of a way for 1st world Yuno to be with 2nd world Yuki, both as a god or otherwise.
Even with considering transferring god powers (Deus to Minene) and time leaping as a god (Murumuru 1st & 2nd), there really is no way for them to be together as gods or without the world ending on them on July 28th.
I guess the author had the same problem and was like, 'fuck it, Yuno is awesome and she'll break the time-space causality with a biscuithammer. Also, Deus will make both of them gods. yeah, sounds about right /troll'
Good ending is good. There really was no other way for it to have a 'Happy End'