just a thought

It would be quite cool if he would try all sorts of thing like previously mentioned voodoo rituals, shamans, electricity, trading places and so on however it would all fail. And in the end it would actually be something very simple like going to the afterlife "clerk" with the correct paper and asking for a correct stamp of something for his "release" papers (but of course after going through some hellish afterlife bureaucracy or something)

A few ideas

From the direction of your summary, I think it would be neat if he could buy his way into it--kind of using that idea about trading with some goth. Basically you can get the afterlife authority to give you a temporary return, but it racks up your bill like crazy. Kind of like indentured servitude. And maybe while you're on their tab you have to serve some function for them too.

Two possible options:

Some southamerican shamans on the best Carlos Castañeda books typoe, or at some university (I can get space at Copenhagens Royal University) where students together with some crazed professor manage to bring the corpse to life.

In Copenhagen I have a studio, perfect for these scenes.

Don´t think in human terms

To me, it seems strange for a ghost, which is something we do not understand on any other than a fictional level, to conform to the rules created by those who do not understand what a ghost is.

A ghost must have a way to come back to life which we do not comprehend, therefore they are hardly rituals (as we know them) or any science that we know of. The point being - the afterlife probably has its own rules - don´t mix them with ours or our perspectives on things.

I´m not answering, just asking.

The way a ghost comes back to life, must be something that gives the audience a new perspective of life&death should they be lucky enough to see it, and they should never see reality with the same eyes afterwards.

Mr. Lightbulb over my head...

He could posess people as a ghost, a la Deadman, and fell everything, and decide to hide from the angelic authorities and live out the posessed person life and move on to another, but decides to keep paying off his debt

he can earn it back

if he has to already work to pay off the debt he built up in life then maybe he can do extra things , things he doesn't realize earns him this credit but does. Nice things he starts do do unconsciously, and then more and more because they are nice things to do. little things like when someone lost their keys and then they are right there on the counter, changing the lights to green for someone who is running late to work, sticking a $20 bill in someones pocket when they thought they were broke till payday. I dunno, little acts of courtesy that are lost in day to day lives of the living, causing a door to stay open to "hold it" for someone. By doing these things he is really learning what life is about and by doing so he earns the right to come back. Not sure how the actual "coming back" would work , maybe when he had earned the right to come back, learned what life was about he would kinda come to the moment before he had originaly died and how ever he had died would be avoided, then he would meet Anja who was looking for an apt in his building obviously his isn't available but maybe she gets one across the hall and they go from there living their lives together and sharing with others by both doing little random acts of kindness

Circle of life

Maybe just assume that we all get reincarnated again and again. The system could work so that as you work of all the sins of your previous life, you could from time to time check at the Reassignment Office what your status is: a lot of sins still to pay for -> you can instead choose to go back as a rat etc. Once you get closer to paying it all off, you can choose to be reborn as a human baby, or work it all of and just sort of fade away to nirvana/ heaven, now free from the circle of life.

Two ideas (or maybe three)

Jack Malinowski already said my better IDEA briefly:

"Also, Could Bruno give up on the impossible by realizing he has to get
Aja killed... perhaps get her to commit suicide on a particularly
depressing evening... This could be heavenly funny material - "

I just thought about it through ANOTHER IDEA. I thought that Bruno could stop working on his debt in order to wait for Anja / stay with her rather than get to Heaven. Of course this would have the drawback of how long should he wait then?

This could be solved backwards to 'how come back to life'. He could A) make her commit suicide B) kill her C) he'd just wait and wait and wait.

A) has the minus-side that he would have to make her love him BAD so she would be ready to do this. and find a way to tell her this. Spiritism could work or maybe just have him tell her while in another man's (rather multiple men's) bodies.

B) has the plus-side that it's easier to do, BUT.. Anja might not like this. Maybe she could like it a bit more if, by killing her, he would save her from a HUUUUGE debt in the afterlife (tm).

C) How to make waiting interesting? And she could get old and wrinkly EWWW! (Maybe this could be comic though.. He would wait and then, in the end, she would turn up a wrinkly old woman (him being still his young self).

ALSO:
Had a little thought about underground economy for the ghosts. He could work for some slimy guy and buy something else rather than pay off his debts: Maybe a place in Anja's dreams? Maybe even a chance to come back to life. I didn't think this through, though :-/

Gaining libido

Here's something:

Bruno finds out that when a ghost is in love with a living person they slowly gain back libido by doing those silly repetitive jobs. When ghost has a fully working libido he can return to the living.

The point of this is that when Bruno is alive again he has to win Anja's heart so that he can be permanently alive. If he doesn't win her heart then he is thrown back to Afterlife and his libido is dead forever.

Just a thought :)

How to come back to life

Okay time for me to wind up my clockwork mind. I'll give you some plots.

1) Bruno is brain dead in a coma, his last will and testament requires that he be kept alive for X amount of time. You could add tension here by giving him a time limit to appeal to a higher authority. Either directly or indirectly (i.e. he knows he has to make up for his sins by posessing people, and doing good deads).

2) The spirit is said to live in the brain, however the spirit could live in the heart, and as an organ donor Bruno's heart gets transplanted into a dying man. The unknown man dies on the operating table, and when his body is revived Bruno is there instead. This could be interesting as the spirit of the man and Bruno's spirit could pass by each other in the exchange.

3) Bruno simply manifests as an act of God, no explaination he just does it. God works in mysterious ways. Naturally God likes to cover this kind of direct intervention up, so the knowledge of Bruno's death is absent from history.

4) Bruno wakes up, it was all a dream... or was it?

Regards Charles