+1 for internet-assisted tag updates across multiple albums, with an efficient way to step through and accept each possible change. This would vastly improve tagging productivity and really help Mp3tag be superior to other competing applications.
Current album-by-album tag search methods are very time-consuming. I have hundreds of albums, so I've given up doing much with most of my tags. I don't know how difficult this would be but it seems very valuable to many.
I'd pay for this capability, especially if several tagging databases were searched simultaneously and reconizing that several of the best tagging databases are not free. I like how dBpoweramp does internet-assisted tagging, but its only available when ripping. The fee for that capability within dBpoweramp was previously $5 annually, but now is bundled with the application license. I'd pay that or more for this feature in Mp3tag.
Perhaps offer a free version and a premium version of Mp3tag that adds this capability.
Florian, what would it take to make this attractive to you? Perhaps conduct a poll to address what you'd need to make this worth your effort?