I know I know you want everything. You can't get everything. The past 4 years I see people complain about the avaliable memory, to updates, not coming fast enough when compared to Google. Among other things...
I believe moving features to Goodlock is the right move if you want fast updates. The closer the firmware is to stock Android the quicker you'll get those updates. This also reduces Rom size as well as allow features like seamless updates possible. If you want those features it's there for you to download. Android started to go modular from 4.0 to now and why updates happen quicker now than over e decade ago. If Samsung is doing this to their software and cut their update times for a lot of devices I bet a lot more people would be happy. People who don't use certain features and want that space will have it. Those who want certain features can still have them. Of course it may take them more time to develop and maintain those features once the new updates are out.
You can expect them to constantly support older software. Some changes are out of their control at times. Like lost licensing or expiration of agreements. Google rule changes for the Play Store to stay on your device.
Suppose you need a reminder every Tuesday at 9 am, 9:30 am and 3pm. It is possible to set 3 different reminders to do the job, but it would be neater to have one reminder with several "alerts" or "sub-reminders" (just like in Samsung Calendar events alerts, or the iPhone Reminder app).
