Yeah, but we had the basically 'fashion accessory' sort of familiars all the way back in 1e IIRC. They were pretty much useless. Sure a few characters once in a while would use the 'find familiar' spell, but it was actually a DISADVANTAGE overall to have a familiar. There were a number of flaws with the whole mechanic.
1) The familiar added some minor static bonus to the PC which was moderately useful to a low level character but effectively trivial at anything beyond 5th or 6th level.
2) The idea of having a 'familiar death penalty' was just a bad idea. It was supposed to encourage players to protect the familiar, but that just effectively means the PC is now burdened with the task of defending the almost helpless critter instead of getting on with adventuring.
3) The critters themselves were quite weak. That's fine at low levels, you obviously can't have a familiar that is way more powerful than party members. But the familiar HAS to be able to scale at higher levels of play. Its defenses (and possibly bonuses and attacks) need to remain level appropriate as the PC advances to higher levels.
If you examine the MP beast master class feature for rangers all of these sorts of considerations have been factored in. The beast gets stronger at each level. Beast oriented feats allow the beast to have a role in combat and provide both fluff and a channel through which the character can exercise his/her role.
Familiars probably do need a bit different sort of mechanics than the beast master mechanism, but it can still serve as a model for the correct approach. With the beast master the beast IS the focus of the character. In effect the PC is the combination of the beast and the character itself. Thus you have mechanisms like shared actions and such.
I see familiars as being a bit less the primary focus of the character and more as being 'some help you receive from higher powers'. In that vein the familiar should probably be more independent and operate more like an extra NPC 'henchman'. In other words it should probably have its own set of actions, but in return it doesn't necessarily fall under the complete control of the character. He can set it tasks, but it will generally act on its own initiative and may or may not do entirely what the PC desires. It may even do things entirely on its own and possibly even at cross purposes with the PC at times.
So, in the vein of being somewhat like a beast master class feature I'd think maybe a familiar would also be a class feature. Straightforwardly a warlock or wizard could exchange implement mastery for a 'magical companion' feature. That would present a reasonable tradeoff. As part of the class feature the character can summon the familiar, pretty much like the beast master does. Technically it isn't a 'ritual', but it has the same overall result.
Once the familiar shows up it is just pretty much an NPC under control of the player and subject to whatever limits the DM wants to put on what it will or won't do. At each level the familiar gains some hit points and it will also obviously have to have some sort of level adds for its defenses as well. It can also act as a 'companion' magic item slot holder for the PC and there could be some magic item variations available to buff the familiar.
Once a PC has the 'magical companion' class feature you can now provide a set of feats ala the beast master ones, but probably toned down and with a different overall thrust. The PC could be able to use the familiar as a point of origination for some powers, gain extra sensory capabilities (see through the familiar's eyes) etc. One or two of these could be tagged with feat powers that either give the familiar itself some kind of attack buff or give the PC an ability to do something (maybe something like if you had a spider familiar you could add ongoing 5 poison damage to an attack or something like that). Another dimension would be emphasizing the familiar as a 'channel' by which a warlock interacts with his 'patron'. So perhaps there can be something working along those lines, especially in the paragon and epic tiers.
Primarily I'd see familiars as especially suited to warlocks, but it could also certain work OK with other Arcane classes.