That's something that you'd need to apply to all pension holders across the board. Would it apply to any jail time, regardless of crime? Does it also apply to spouses or ex spouses that were otherwise entitled to a percentage of it?
Treating police as military would extremely exaggerate the thin blue line. Separating them further from civilians would exacerbate these problems. The places where these problems are the worst already have a mentality of us vs them, as if they are waging war against the people.
Civilian courts are absolutely not cutting it. We need greater oversight. The prosecutors that rely on police for gathering evidence are less likely to pursue charges against those officers. They are given the benefit of the doubt nearly 100% of the time. That's a bad precedent that sends a dangerous message.
But I have another point to consider against your military argument. And that's that the military looks out for one another. At every level the military attempts to cover up and downplay negative actions. From small screw ups to major crimes, a unit doesn't want the negative publicity/reputation. If a private forgets his weapon, his sergeant would rather exercise him until he regrets being born than file paperwork with his commander. It would be a poor reflection on both the private and the sergeant and would follow both for quite some time, so it's best to deal with it internally.
Unfortunately this is also often the case for larger crimes like rape or assault. It plays out even more so when dealing with 'the enemy'. Soldiers look out for each other. They have to to stay alive. Unless one of their own really goes off the rails and is a threat to other soldiers, he is unlikely to be turned in. There are movies about this that are based on real events. When a soldier accidentally kills a farmer, his buddies will testify that they feared for their lives. That's if the incident is every reported in anyway. In a foreign country during a conflict, a lot of incidences are casually overlooked. It's easy to write them off as 'war is hell' and move on.
That mentality is already too pervasive back home. A lot of police are veterans, who bring their training and mindset home with them. At best they see fellow citizens as 'civilians' and at worst as 'the enemy'. Which serves to justify whatever means necessary in gaining compliance and enforcing the law.
Civilian casualties are an acceptable consequence to war. A necessary evil that maybe should be minimized, but cannot be eliminated. Some innocent farmers have to die in order to secure freedom and democracy to the rest of the country.
That parallel would say that some babies have to get flash banged in order to protect the populace from marijuana. And that's absurd. Indefensible.
I'm not saying that that is what you are advocating, I'm saying that I fear the consequences of such a move.
The thinking in a war zone is that if a soldier hesitates to pull the trigger, he can cause great casualities. If he mistakenly kills a farmer, that's something that any soldier could have done, so the rest don't want to see that one hanged for it.
At the highest level, reporting civilian casualties shifts public opinion against us and makes it more difficult to win the war. Sergeants and generals are equally motivated to look out for one another.
The cases you hear about are the extreme cases, like that guy collecting fingers. If you read about it even they didn't want to turn against each other initially.
UCMJ isn't all that effective. On the other hand, when CID or JAG (the military's arbiters of justice) ARE made aware of infractions, they usually drop the hammer. CID and JAG are looking out for the best interests of the military as a whole. CID could maybe be compared to the FBI while JAG would be DOJ? They're only called in for the big cases of extreme corruption.
I'm rambling a bit, but I hope that maybe some of this makes sense.
An external oversight group that actually has the power to make changes, and who's only motivation is to disrupt institutionalized corruption, is the best chance of stemming the tide.
An article a couple days ago highlighted that only 1 whistleblower out of 400k NYPD spoke out about their poor practices.
Incentivize whistleblowers, maintain rigorous standards, and force departments to allow oversight, inspections, and investigations.
The DOJ has been conducting investigations into a small number of the most serious areas, and only after considerable petitioning and outcry. It's not enough, but it's the right move.