I have more problems seeing Clark with someone else after he met Lois than I have with Lois seeing someone else, but only because Clark admited falling in love with Lois at first sight.
He knows he loves her, he knows how much and how deep this love is, and if he does know, being with someone else might mean betraying that love as well as the person he is with. On the other hand, it took Lois some time to realize her feelings for Clark and admiting them to herself. So seeing her with another man is far more believable, not to mention confortable, to me. I don't have problems seeing Clark with someone else as long as is either before he meets Lois or is just casual dating(specially in season 1).
If Clark decides to have a serious relationship with someone else, for any reason(Lois is married, dead, missing, doens't love him, ...), after all, I don't want him to be alone, I would have to believe that he loves this other person just as much as he loves/loved Lois(even if it is not the same kind of love) and he should tell this woman how he felt/fells about Lois. If he doesn't, it may seems that Clark is just using one to forget another or that Lois never meant as much to him in the first place.
The kind of love I believe Clark feels for Lois and Lois feels for him doens't die only because the person you love is no longer there, is not avaiable or doens't love you in return. And I can not accept that Clark would start a new relationship too soon, regardless the reason.
Clark is an unique man with an unique life, and he sees the world in an unique way. Trust would be a major issue to him and even after being with Lois and knowing it was possible for him to have a normal life, it would be dificult for him to let go and move on, finding a person he could share his life with, so I believe he wouldn't start a serious relationship only because he can or doesn't have Lois. (and this is just my opinion).
Every time I read a story about Clark being with someone else I ask these questions: Can Clark love someone other then Lois? Yes. Can he love someone else as much as loves Lois? I don't know. Does he loves this woman as much as he loves/loved Lois? If Lois shows up avaiable and loving him, what will he do? Will he stay in a relationship knowing he loves Lois more than the person he is with? Will he stay in a relationship only because he believes is the right thing to do? If he knew he could never love this person as much as he loves Lois, why did he start the relationship in the first place?
What about Lois? Can she be with someone else after loving Clark? Can she really love someone just as much?
Anyway, if it is well-writen and a believable story I will read.
