I was actually thinking of energy tiers like cable conductor has main influence on cable losses...
That's an interesting idea actually; so we have the large majority of the resistance/loss from cables being based on their metal type, which is then fortified by their insulation/covering? Seems like an interesting mechanic, but I don't know how complex that is to do in Java, and there's likely a large priority list before any kind of power transmission revamp at present.
Not sure what you mean when you describe the function of dense or 4x cabling though; you say the packet sizes stay the same (Ok, fair enough), but it allows for a transmission rate four times that of regular cable? That I can get behind, but I don't know whether that might be imbalanced or not. I mean, you get the same EU/t transmission from the next 'level' of material, but it might allow larger packets or have less loss in transmission.
in lossy order [most lossy] iron->tin ->bronze->gold->copper->silver->graphene[almost losless]
Concerning your material resistivity flow chart, I see nothing wrong from a real-world-translating-to-minecraft point of view; however in terms of gameplay, I'd change a few things;
1) Either move bronze up to be better than both tin and copper or scrap it completely. I don't see anyone putting the effort in to make bronze cabling if they can just extrude copper (or tin, if it were better) instead; less effort, better results, and I'd say wasted programming time coding an item I foresee few people using.
2) Maybe keep gold above copper in terms of conductivity; it doesn't make sense from a real world standpoint (which probably makes all the Power Engineers that play this mod and others with similar transmission systems somewhat irate [IT MAKEZ NO SENZE]), but similar to the current system, gold is (at least before you obtain an advanced miner) slightly rarer than the other metals; thus making its use more valuable if it can transmit more power, or have more conductivity than other more common metals (I'd say iron is the exception to this only because you use so much of it to make other machinery anyway, to then have to use more ingots as cabling is just a kick in the nuts. At least before you obtain an Advanced Miner).
3) I'd be tempted to say take silver out, if only because IC2x (on it's own) doesn't have silver ore as part of its worldgen (making it a rare, end-game (mid-game?) resource), but I'm pretty sure myself and others that play without a mod that worldgens Silver Ore are in the minority. Leaving it in, I'm also seeing silver as a 'cheaper' alternative to graphene, assuming graphene is made as hard to make as Glass Fibre is now; if it's just basically a type of coal dust wire then that may end up being easier to make, at which point silver cable runs into the same problem as bronze (more productive to make the next level of cable).
I also like the idea of being able to colour the cabling, but only in that it would seperate different lines by colour. I find playing AE2 that it's often easier to separate sub-networks via adding quartz fibre between cables then colouring it instead, but it's two different ways to the same solution; I don't need to differentiate the networks visually, I just need to separate shortest paths for channels. My personal preference is still for example using the wrench to enable/disable cable connections on a side, but honestly if the painted cable was implemented I don't think I'd complain (only when I have to colour a line last-minute because my planned layout didn't take into account adjacent cabling :P), but I think it would be wasteful coding if they implemented both for the sake of community happiness (assuming more people want one or the other).