Lack of support for multiple audio streams.
MC certainly supports multiple audio streams, and selection of the stream you want, when multiple streams are available on a DVD or Blu-ray. I can't test your situation because I don't have any TV channels that support multiple audio streams. This stream selection capability may not work with TV broadcasts.
You can select from available audio streams using the OSD (On Screen Display) or the Right Click menu when the program is playing. See that attached images.
The stream that you select will be saved in the "Playback Info" tag. You may even be able to use a tagging rule on a Recording Rule to set the audio stream.
Bouquets.
This is supported now. It requires a little bit of work to set up, but the capability you want is fully supported. Imugli split the question out to a new thread, so I have described how to do it over there:
http://yabb.jriver.com/interact/index.php?topic=101884.0Subtitles. Transmitted in data stream or pulled out from teletext.
I suspect that the America format of Closed Captions is supported, but I can't confirm that as I'm in Australia. The European and Australian format that uses teletext data in television broadcasts isn't supported yet, but I believe it is still on Yaobing's list of things to do. I suspect that a bunch more Europeans need to ask for it before it will get some priority.
A feature that should be there, but aren't yet:
-pulling EPG from data streams. Every TV and STB can do that, but in JRiver I have to load an XML file, that I have to find on the internet...
MC can pull down EPG data from ATSC broadcasts in the USA. Covering the rest of the world is also still on the list.
In Australia I use
EPG Collector to pull EPG data from the DVB-T stream. It works very well, can use satellite, cable and terrestrial. I know there are users in the Netherlands, UK, and some other parts of Europe. It is worth investigating for your needs. It isn't perfect, but provides whatever data is available in the stream. I am working with the developer at the moment to improve the output of its metadata lookup feature, which finds Season and Episode numbers of TV Series when it is not included in the stream, in addition to other metadata, by looking up TheTVDB and TMDB.
Of course if you are in a location supported by Microsoft EPG data, the mc2xml version built into MC will downloads the EPG data for you and loads it into MC, fully automatically (once configured) and all free of charge. No need to go looking up other internet sources. Note that the Microsoft EPG data is now provided by Rovi, at least in the USA, and probably other locations, but I don't know if Microsoft has rolled that change out to all location yet.
Subtitles downloaded from net
Provided by the third party
Subtitle Downloader plug-in. I haven't implemented that one yet though, so can't comment on how good it is. Read the thread.
Watching/recording multiple channels on the same transponder
Still a possibility I believe, but not a priority. Probably still on the list. I just bought a four tuner card and haven't needed to worry about running out of tuners . . . so far.
Transmitting tv channel over network & conversion on the go (eg. .TS to .MP4)
Answered by Imugli. Already there. Some limitations.
SoftCAMs
No idea. Probably not.
Storable teletext
MC doesn't use teletext information at all as far as I know. So no.
Channel's icons
Answered by Imugli. Watch the build threads of the next few releases.