You've hit upon a potentially interesting administrative law issue here, nereo. ;) Not because of the Form per se, but because of what I discuss below.
If the only issue were the Form, the solution would be to write "see attached statement" in the fields for the employer's name, address, etc., and then explain that you have multiple employers in a written statement attached to the end of your tax return. The reason that the IRS does not want you to file multiple copies of the Form is because that might result in you incorrectly computing the numbers, not because there's a rule against providing clarifying information on supplemental paper.
However, the usual solution doesn't work here because of a problem with the Treasury regulations. Here's the explanation.
The foreign earned income exclusion is found in 26 USC § 911. In particular, 26 USC § 911(d)(9) authorises the Secretary of the Treasury to make regulations "as may be necessary or appropriate to carry out the purposes of this section". One of these regulations is 26 CFR 1.911-7(a)(1), which says that in order to receive the foreign earned income exclusion, you must attach a statement (either Form 2555 or "a comparable form"), which must contain "[t]he name of the individual's employer". The regulation does not appear to contemplate that a person could have multiple employers.
There are really two possible ways to approach this.
One approach would be to conclude that the regulation does not allow you to take the exclusion unless you have exactly one employer, because otherwise you cannot comply with the regulation. If that is the effect of the regulation, then the regulation is probably void, and you would (1) ignore the regulation, (2) attach a statement listing all your employers, and (3) attach Form 8275-R (Regulation Disclosure Statement) to your return to explicitly state that you are ignoring the regulation.
Alternatively, you could assume that the regulation actually allows multiple employers and, again, attach a statement listing them, but not include Form 8275-R since you would be complying with the regulation.
Discussing the tradeoffs of the approaches is very complicated. While I could write more later, you may want to retain counsel if you are concerned about this.
