^ I've never been to a theater where they were gaming. If this is a gaming build that's all the info that needs stated.
Most people don't need all those "options" you imagined, which is why HTPC cases aren't the same dimensions as desktop cases. Upgrading or repair to them is about standard mobo and PSU form factor which the silverstone has. Array of HDD is totally unnecessary unless explicitly stated, that's what a NAS is for, and the more mechanical things you have in it, the more noise from them and the fan forced airflow rate needed to remove heat.
If you have the space why would you want it skinny? Because it looks better, and because you'll still have more space remaining which is better for airflow without increasing noise, and I don't just mean airflow for the HTPC but spacing of other HT components too.
Maintenance? No difference. Maybe you're thinking about tiny tower cases instead of horizontal ones. The only difference on the Silverstone is you have to unscrew the frame that's (optionally) holding the optical drive in, to remove the HDD IF you put one there instead of only one behind the PSU or an SSD alone.
There's nothing especially proprietary about a half height mATX case that takes a standard (full sized) ATX PSU. It just comes down to what I asked which was whether it's HTPC or gaming so you'd need more height for a gaming video card. Other than video, there are lots of options for half height cards for other functions. HTPC isn't a new genre any longer, and people don't tend to upgrade them nearly as often unless moving from 1080p capable to 4K which I also mentioned previously.