I've been thinking for some time how hard it has to be to balance all of the skills that exist between classes and among class builds as well weapon, mages guild, fighters, etc. One of the problems with the passives system as it currently exists is that we keep piling on new passives as time progresses. Our active skills make us choose our build, but passives have a way of continually making us stronger and stronger. I believe it also makes it harder for balance between passives and skill sets to exist. Secret World resolved much of this problem by forcing players to slot passive skills into a passive tray. I think 5 passives would be too few for ESO, but I'm sure some reasonable number could be concocted for this. If we had to pick and choose what passives we slot, I think ZoS could control the balance of the game a lot more easily. There could even be more than one tray for different uses, like you could only have 5 slotted 'utility' passives, or 'damage' passives, or 'mitigation' passives or such. Take the legerdemain skill for instance. You might have all passives filled with your skill points, but perhaps you only use the bulk of them while you're going on your thieving run. When you head to cyrodiil you'd pull some of those passives off in favor of some of your fighters guild passives. That's the core of the idea.
US/AD - Dodge Hopper - Vet Imperial Templar | US/AD - Goj-ei-Raj - Vet Argonian Nightblade
US/AD - Arondonimo - Vet Altmer Sorcerer | US/AD - Azumarax - Vet Dunmer Dragon Knight
US/AD - Barkan al-Sheharesh - Vet Redguard Dragon Knight | US/AD - Aelus Vortavoriil - Vet Altmer Templar
US/AD - Shirari Qa'Dar - Vet Khajiit Nightblade | US/AD - Ndvari Mzunchvolenthumz - Vet Bosmer Nightblade
US/EP - Yngmar - Vet Nord Dragon Knight | US/EP - Reloth Ur Fyr - Vet Dunmer Sorcerer
US/DC - Muiredeach - Vet Breton Sorcerer | US/DC - Nachtrabe - Vet Orc Nightblade
EU/DC - Dragol gro-Unglak - Vet Orc Dragon Knight | EU/DC - Targan al-Barkan - Vet Redguard Templar
EU/DC - Wuthmir - Vet Nord Sorcerer | EU/DC - Kosh Ragotoro - Vet Khajiit Nightblade
<And plenty more>