What you are asking for isn't even supported in Windows Phone... As far as the update goes, T-Mo doesn't have one in house at the moment, so start asking Nokia for it (since they have sold about 50k of the 810's, it's probably low on the list - especially since the 7.8 updates are starting to be readied for rollout)... It's funny how the updates were going to be pushed OTA from Microsoft, but not all the devices got it at the same time, nor is it available for all devices right now. Something to remember though, I haven't had any off the issues like the random rebooting that many had with WP8 so I'm not needing the update quite yet.
Now regarding the update - there will be no WiFi calling app - just like the Radar and 710 before - because there is no demand for it. T-Mo sells 50 Android phones to every 1 WP device. Heck, there are more iPhones on T-Mo than WP... WiFi calling was done up for Android because the bones were already done by SIPDroid and GrooVIP... Sure, they could use Skype's backbone and run WiFi off that, but, again, for the limited number of devices, why would they bother?
As far as the storage goes, you must be from Android in the past, because installing Apps to the SD card will not be coming to WP anytime soon - or ever for that matter. There are too many issues with cards kicking the bucket, installing incorrectly and having read/write issues to even try that at the moment. As a matter of fact, I've had to repair my SD card 3 times now, and that's without ever removing it (except to fix the issues) and just restarting the phone.The basics of internal storage on this thing is that 1.9GB is system software - around 2GB is reserved "other memory" - this leaves around 4 for Apps and Games... Considering the larger games are .5GB, you won't have much room left after installing a few. Apps on the other hand, are pretty small for the most part so balance is important for limited memory handsets.
Hopefully you can see that the 810 is really an entry level phone, that hopefully you didn't pay $150 for on contract. This is why so many people were recommending the HTC 8x over the 810 - internal storage nearly universal updates. While I do agree that Central should get their records straight and get us our listing easier to manage, again, it's not a deal breaker for me.