Air Strike
The concept of a Ukranian air strike on rebel positions from under MH 17 is completely unfounded.
Firstly, a SU-25 can barely keep up with a B777 unloaded and loaded down with armaments can't climb above 16000 feet.
Secondly, if you read the transcripts of the Russian ATC operator at the time he/she clearly states that they see nothing on radar apart from MH17 itself breaking apart and the two other flights in the general vicinity. The Russian presentation about the radar data is a blatant propaganda sell with the "other" target just being the predicted track of MH 17 and the "actual" target being the aircraft itself breaking apart. So there is absolutely no doubt that any of the SU-25 theories are false and all have originated from Russian/rebel sources in any case.
As for the rebels not gaining anything out of the shoot down I agree. It is pertinently clear that they were not intending to down a commercial aircraft and did it by mistake, albeit recklessly.
I don't envy the dutch criminal investigation team trying to track down the perpetrators. There's every chance that whoever launched the missile was trigger happy and did it without exercising due diligence. If so there's a fairly good chance that the BUK crew have probably ended up buried in a ditch somewhere and will never be heard from again. In that scenario Russia needs to be held responsible in my opinion for supplying the rebels with SAM weapons (if they were indeed provided by Russia).