While it's probably not common, I have had a few worlds start with no rubber trees for miles. (I tend to use custom terrain generators, so this might be a factor; it's tangential to the point, however.) As the development history of IndustrialCraft points out, the real progress of electrical power included a decades-long stage where wool wrapping was the way to insulate wiring. It failed when wet and was flammable when dry, but technology managed to progress without killing half the population, even so. A recent world seed really brought this to the fore of my attention: tundra and taiga as far as the eye could see, and exactly one rubber tree within a 1km radius of the spawn point. It dropped no saplings. I managed to get exactly enough rubber out of it to wire up an extractor for taking advantage of other resin that never materialized. This wouldn't be such a big deal if uninsulated wire had any use whatsoever, but let's not kid ourselves: 90% of IndustrialCraft's material is entirely inaccessible without insulated copper cable, making the unreliable rubber tree a potentially crippling bottleneck for the entire mod.
To alleviate this problem, wool insulation should be brought back, in a limited capacity. Rubber is unreliable, but sheep are eternal. Surround a copper cable with four wool blocks for an insulated copper cable, or an ingot and eight wool for two. It's less efficient than rubber, and that's part of why we don't use it anymore out here in the real world. It's not sturdy enough for the levels of current more advanced cable carry, and shouldn't serve to replace rubber there, but at least this option would let people build themselves up to a macerator without the tedious, almost cliché search for a swamp to start building in.
Things I've realized:
* You only need to kill spiders for string until you have a generator and a macerator.
* There are way too many advanced machines that don't need any rubber at all except what's on Insulated Copper Cables.
The solution to this is better laid out on FenixR's Suggestion thread here . If gold is used in more of IC's advanced machinery and requires actual rubber for that purpose, Wool-wrapped Copper Wire can be an item completely separate from Insulated Copper Cable, and used in alternative recipes for:
* Rechargeable Batteries,
* Luminators, and
* Basic Circuits.
Thus, one item and four recipes would unyoke most basic technologies from the tree sap oppressor, at minimal cost to coding and computer resources. The MV Transformer would not get an additional recipe, as this is a high-voltage application requiring much sturdier and better-insulated cabling. Essentially, between the insulation and gold changes, you will have to track down rubber eventually, but you can at least equip yourself and start to build a home before you do.