I will give an alternative view, my view on this
Also having spent years trying to find a comfortable solution, i came to the conclusion that micro comps (pretty much all of them) are just not suited very well to the FE ethos - ie, click a game and run it.
Mostly when people speak of a front end (especially in retro gaming terms) they imagine a system of which you browse a list of games, you press a key/button and you're off playing. This works really well for closed systems/consoles, but it somewhat falls apart when it come to micro's, due to the nature of these machines. There is no standard to follow, no rules to adhere to because these machines were the pioneers, they established over time, what we now would call "standard".
Not only do they have their own rules per system, but they also have their own rules/commands per game/software! This is why, to this day, no one has made a definitive solution to this.
There have been many valiant attempts to standardise micro's, as outlined by you @Macguvyer, and while they make things a little easier for us all, they will never be perfect. It's just the way the water flows.