I've posted this on other forums, but the common misunderstanding is that static linking is prohibited under the terms of the LGPL, it is not.
Section 6a provides a provision which allows static linking provided that the developer provides (binary) object code, or an offer to do so for a period of 3 years, which may be re-linked with the LGPL components.
Regarding app bundle signing restrictions, these are prohibited by the GPL, but the LGPL allows you to distribute under "...terms of your choice, provided that the terms permit modification of the work for the customer's own use and reverse engineering for debugging such modifications."
If those terms comply with 6a, i.e. that you provide access to unsigned object code in a form which may be relinked, modified for the users own use etc., then there doesn't seem to be a conflict.
6b specifies dynamic linking, but it is only one option in section 6.
Whether 'permitting modification' refers to the actual app bundle, or the components provided under 6a is to my mind an open question. If it were so, then 6a would be invalid regardless. The prerequisites for doing so would be an apple developer account and apple's tools / hardware etc, but under the terms of the LGPL and GPL, the developer is not required to provide these.
Of course this isn't legal advice.