Until now packagers didn't had to wonder what technology to choose GTK had to be preferred over Qt when both were available.
With the (still unofficial) inclusion of KDE, the update of the Qt stack to 5.9 and the future migration of Budgie to Qt, it might become confusing, especially to new packagers. Also other questions might pop for example: if gnome keyring support is available, we enable it but KDE uses kwallet. At the moment, I don't think kwallet support should be enabled for non "k"apps, but what shall we do if/when KDE will be officially supported ?

Perhaps it is still too early to have such a discussion now, but defining some guidelines when the time will come would be a good idea.

Another thing that bugs me sometimes concerns the choice of the licenses. Many applications give the choice between several licenses at your convenience. Personally, I prefer GPL-2.0 over GPL-3.0 and LGPL over GPL... I guess the choice doesn't really matter BUT I sometimes see people setting multiple licenses instead of choosing one of them (for example Perl libraries often offers the choice between Artistic or GPL and it's not rare to see both). In the opposite, when an application is bundled with 3rd party components under a different license, the license of those components is not added (because not mentioned in the main COPYING/LICENSE file). Nowadays I try to be careful with this but until not so long ago, I even didn't think about checking this (and I am sure I am not the only one!).