How to use remote Ivy artefacts in Maven jobs with different binary repository managers? Consider the following situation:

Alice -----              { Firewall }  Bob
|                                       |
Artifactory / Ivy repos  -  ---   --- Nexus / Maven Repos


That is, Alice uses Ant and Ivy to publish her artefacts in an Artifactory in Ivy repos, while Bob sits behind a firewall and builds Maven artefacts storing them in Maven repos in Nexus.

How can Alice provide her artefacts to Bob? (while both do not have to make large changes to their setup)

So far, I have considered the following options and decided to ask you before trying them out:

(1) Bob manages credentials to access Alice' artefacts in his build system and uses a Maven plugin for Ivy (which means configuration work for all relevant projects)

(2) Alice uses an Ant/Maven task to generate POMs for publishing/deployment step and offers an additional Maven repo, because Artifactory can support it different repo formats. This for Bob's most convenience though Alice needs to do configuration work of all relevant projects and there might be also other Bobs in future using other binary repository managers.

(3) Bob configures Nexus to be a proxy for Alice' Ivy repo (which is AFAIK was not possible as of 2014).

What would you do?
I'd go with (2). Since Bob has a more rigid setup (requires Maven metadata), and Alice can provide that (using more flexible Ant), that sounds like the easiest way to go.