What would you like to see added in FreePBX 15?

There are 2 general classes of Cisco phones - the SPA series that are SIP and the Enterprise series which can be ordered either with Skinny or SIP. I think the Enterprise series with Skinny are the ones you are talking about. Not sure what you mean by “normal firmware” here. The end user wouldn’t know the difference. And the SPA series are really old Linksys product that’s been gussied up. Cisco is positioning to sunset that line anyway and use their new multiprotocol phones. I’m not sure why you would think anything about the experience would be different - what more do you need in a desktop phone than the ability to dial, search an ldap directory, have a message waiting light, and plug in a headset. And the Cisco phones can be made to do that even if for the Enterprise phones it appears to be as kludgy as getting the Aastra 6753i to do it. Since you can define buttons on the phones how you want, it seems to me that for the SPA series at least they wouldn’t be any worse than a Yealink.
Oh and that is one other thing that should be in Endpoint Manager - a firmware library for phones. (I don’t know if one is in there or not) but it sucks to have to root around all over the Internet for firmware for phones.
It appears to me the biggest advantage of using the Sangoma phones is plug and play. And yes I know there are people out there who don’t really want to understand the in depth of the products they use and if they were going to do a cheap and dirty system they would be well advised to setup a FreePBX system with the free version of Endpoint manager and Sangoma phones. Then its just WYSIWYG for them and they don’t have to understand provisioning and button assignments or any of that icky stuff. But I don’t run that kind of business. What is the fun of IT when you don’t know the stuff works that you are selling?
Seriously, though, I can’t help but point out that you lack an Android softphone. I’m currently using the last beta version of CSipSimple. It works really well and doesn’t have NAT issues and all of that. But when I tried it out on an android version newer than 6, it crashed. And of course it lacks directory lookup, message waiting, and so on. Video does work on it after a fashion. Sangoma could do a heck of a lot worse by picking up that code and forking it into your own softphone app and I have to say that if you really want to be in the business of selling phones, both iOS and Android SIP softphones are so lacking, that if you had a really good softphone app that’s the one phone I’d be in the front of the line to buy from you.