Well, one other thing to consider, is that the things that would drive Keiichi and Belldandy apart are NOT things under the control of the Yggdrasil system once it has been restored.

Option 1:
Yggdrasil's Ultimate Force is able to keep things under it's direct control [AKA, Mortal Obstacles] but obstacles being put up by.. ya'know.. other Goddesses... the CEO of Hell... ect. are WELL beyond what that system was intended to work on.

Option 2:
Perhaps between the sheer will the Ultimate Force system was having to put into place due to the attraction power of Belldandy's Charisma to keep the two togeter, Heaven had to make their relationship an exception to the Ultimate Force system too keep it stable, feeling that with the three Goddesses of Time around him, they would do a much better job of handling the situation * snicker *

Option 3:
They don't need the Ultimate Force system anymore. In the beginning, Bell and Kei's relationship was on shaky ground on both ends. After the Ultimate Force was brought back online, that situation had dramatically changed. Keiichi has his full trust in Belldandy, and loves her to his core, as she does for him. Because of this, they don't NEED Ultimate Force to step in, because they will weather through it like any two people who truly love each other.

I personally think it's Option 3... but it's a few reasonable [IMHO] options.

~k1

I found that strange as well. For it being the Ultimate force it is very limited.

But I agree with keiichi000 that they don't need it anymore.
But as he pointed out in option one that Yggrasil can't directly control all beings, ore prohibit the interference of Hild is also reasonable.

All though I still think that Kami sama has something to do with it though.

The concept of the Ultimate Force was dropped agter Belldandy revealed that she was on earth on her own free will, which effectively terminates the program. Also, for the storywriters, it allows the plot to progres with more freedom

I'm on with that one. After Ygg was repaired, Bell said that as a result of it having been down, all standing contracts had been voided. However, she chose freely to continue to stay on earth with Kei. As such, there's no contract for the Ultimate Force to enforce.

At least, that's what I got out of things. As for why she's allowed to stay on Earth without a contract....beats me. Maybe the Almighty is just being nice. :)

I think the ultimate force purposely set them up together, it did after all allow the wish, and once it found that they could stay together without its interference it backed off.

It never seemed like more than a mere plot device to keep things awkward at the beginning. Once things were established enough there wasn't really a need for it storywise, and if it had continued it would have adversely affected things I think.