On the wire insulation, the story I heard from what I feel is a reputable source, is that the insulation was supposed to be "bad tasting" to rodents and such. Evidently there is more of a rodent problem somewhere in the world than it usually is here in the US, and they were trying to cure this wire-chewing problem by using a foul tasting insulation. That's what I heard anyways.
I am not 100% certain that all 104 engine MAF sensors are identical. I know that on the new V6's and V8's, although they look identical, they aren't the same part. I would venture to guess that a C280 (104) is different than a E320 (104), although the E320 and S320 may be the same. Using that theory, your C36 probably has a unique MAF sensor. I am not aware that the MAF's were available reman.
The hot film matrix is damaged by sand particles, cleaning I don't believe is an option here.
I don't believe there is an economical alternative to what is being used at this time for MAF sensing. There were other ways to determine airflow, but not mass airflow, this is different than just "airflow". I always got a kick out of the first system like this, it was essentially the same but used a "hot wire" type sensor and was called LH-SFI, the "LH" standing for Luft-Hotwire. What you have here is HFM-SFI, which stands for Hot Film Management, the SFI of course is Sequential Fuel Injection. The current ME-SFI is still using the same MAF sensor, the main difference between HFM-SFI and ME is that the ignition system is incorporated into the ME control unit, on HFM and prior is was seperate of the injection control.