I'm a bit of two worlds on Superman's marriage.
To begin, I've always considered there is something intrinsically wrong with his pursuing a relationship with Lois. The reason is simply that she is a mortal. Superman, done right for me, is very Maggin-istic. I am with the god-like Superman. So, from that perspective, when I consider their relationship, it looks more like the Zeus' lust thing, than an honest relationship.
Maybe, this is the little mythical aspect of the relationship that causes it to work on many levels.
For me, Wonder Woman, etc. are all much more appropriate mates to one who could be really a father to a new pantheon on Earth.
But, if we go the route of the humanized Kryptonian - then sure, Lois has got many of the cherished qualities that Clark would look for in a mate, the relationship makes sense.
Ultimately it is really just how good the writer is with the subject matter - if he thinks it's in his way, then it will probably be so in his writing. If he likes it, it will be useful in the story. If the writer shows good insight into the relationship then I'll enjoy it. If he's interested in making Lois jelous - then just end the relationship and let him go after someone else. I just think life would be more fulfilling for the character if he could go about his duties with his mate than without.
I wouldn't want WW to replace Lois ever, but in a world or future without her I see your point and the epilogue to Kingdom Come suggests that in a interesting way. Also I don't think in any version Superman's really been given a ..oh how to put it. A interesting bachlorhood. He's sort of fallen for Lois from day one with any other relationships being before he came to Metropolis or as incidental to his triangle with Lois. This isn't to say I think Superman should be like James Bond. But I think it would be interesting to see some other personalities fall for our Man of Steel or he with them before he chooses Lois as his one and only. In any case Superman would be about having real relationships rather than one night stands.
Just some thoughts...
For the writing I think if they are gonna go with the marriage angle, then Lois actually *could* go on missions with Superman a lot more than she does. I think writers are scared to do that. Maybe because they think it ruins the fantasy for younger or teen-age boys. Perhaps, it's the implication that Superman now has a "sidekick" or thinking that it would be somehow lowering Lois herself because she would be in a sidekick role.
It's obvious she couldn't go on every single mission so it's not like there would be a total loss of solo action with the character. (..and again there's always another title you could use for that). Also, throughout fiction characters have been able to have partners, assistants, etc. who are directly involved in things without taking anything away from the main hero or ending up as the hostage. ..and even if they do that doesn't have to mean Lois has to prove useless and unresourceful. If anything it would be a chance to show that she IS. Make her a real partner.
Maybe to it's that people feel since she doesn't have powers therefore she would be in too much danger so Superman would be stupid to bring her along. ..and sometimes this would be correct and Superman would need to sort of establish boundries in that regard. However she IS a top reporter for a great metropolitan newspaper and her husband, the man she loves more than anything else is risking his neck to save the world and sometimes even the universe. I think for her to want to go along with him is not an indication of her being a harpy or a nag, but of a woman with genuine emotion and feelings. Because I think any human being in that position would want to be at their loved ones side and especially so in a case where being in the thick of things, trying to help or to chronicle is just as much a part of who THEY are as a person as it is part of their loved one.