Weaknesses in UEFA's case in no particular order:
1) Due process.
a) It's supposed to be a confidential process and yet journalists are discussing how confident UEFA investigators are and what their concerns are. Does this matter? It's not like there's a jury, but the biggest problem City have in my opinion is that after years of innuendo, there is now an almost universal acceptance that City are cheats and that UEFA must show its teeth against the rich and powerful or will lose all credibility.
b) If you read the Manchester City statement, we also add that the process has been "curtailed" and we also learn that UEFA 'filed' this on the last possible day, which makes you wonder whether they have actually considered the case properly. The BBC report that UEFA feel that City have not answered issues about deception. Is this because the case is incomplete? City say, "The decision contains mistakes, misinterpretations and confusions fundamentally borne out of a basic lack of due process and there remain significant unresolved matters".
2) The financial value of the "inflated sponsorships".
Both the BBC and NY Times both claimed that investigators feel that City's evidence "do not refer to the more pertinent allegation that they may have misled investigators."
UEFA's first review showed that they did not write down the value of the Etihad deal. And I think that it is unlikely that UEFA can demonstrate that Etihad are a related party. Etihad are the state airline. Their sponsorship is underwritten by the Executive Council of the United Arab Emirates. Sheikh Mansour does not control Etihad Airlines. Khaldoon, City's Chairman sits on the Executive Council but for me the Executive Council just underwrites their financial obligations, they do not control their commercial activities, and I don't see how anyone can claim that they do. The Der Spiegel evidence jut showed how the financial obligations were linked to the Executive Council, they do not show that City can have influenced the commercial value of the original deal.
The smaller sponsorships are more awkward. For example UEFA could argue that Aabar is a related party because Sheikh Mansour is the Chairman of International Petroleum Investment Company which is a sovereign wealth fund which holds a large investment in Aabar. It's a matter of accounting interpretation whether they are related parties, however the collective smaller UAE sponsorships are worth around £15m (I haven't checked that but I am pretty sure the transaction value is in that order).
UEFA would have to show that City's UAE sponsorships are a) inflated and b) related parties. I think they only stand a chance of doing so in respect of the smaller sponsorships, so are they really going to ban City over "£10m to £20m of inflated sponsorship". That sounds wholly disproportionate when City's current revenue is over £500m. I forget what it was then, but it would have been of the order of £100ms
The Der Spiegel news surfaced after City's last audited accounts were released. It would have been an interesting test to see what the Auditors made of these claims of related parties. If I were in City's shoes, I would ask our auditors to review the evidence and submit that to UEFA.
Conclusion: I think UEFA will feel obliged to sanction City based on their image as a regulator and City's media created image as an ogre, but I don't think they have a case. Indeed I think they may have deliberately played this out until the last possible day to file the case, in order that CAS throw it out on the basis of due process thus getting them out of a hole.
If they do their job properly, I think at the most UEFA could stipulate that the smaller UAE sponsorships should be written down, and fine City the difference. It has to be remembered that the whole 'subterfuge' was initiated when UEFA changed the assessment rules at the 11th hour which many people would argue was an act of subterfuge in the first place.
The problem I have is the competence of UEFA, their independence, and the independence of any judicial bodies in dealing with a club owned by Middle-eastern owners. Can City expect a fair hearing? UEFA in my opinion are very weak. I think they are more interested in bolstering a battered reputation than they are in the technicalities of the case. City represent an opportunity for them to become a white knight and on that basis, not the evidence I expect them to ban City, but I expect CAS to throw it out on due process and disproportionate punishment.
This is my reading of the matter without access to the evidence but based on the media narrative and comments coming out of both camps