Matthieu, it is unfortunate. We have (had) a deep integration into our systems where we queried the MySql database directly to generate custom reports/insights and automated analytics reporting via email. We have custom dashboards built into our software and everything.
We also received a slew of calls today from clients that were running their own ads with the same issues. We had the analytics deployed to about 200 websites. Luckily, the way our systems are developed, we were able to remove it in just a few minutes with a global update. If Google decides to allow it, we can restore it with a global update as well.
We had about 60 Google Ads accounts that have been disabled that we were managing (not counting the customers managing their own).
We have not yet had our Google Ads accounts re-activated. I will update this forum once I have more information. Waiting to hear back from their support on both the re-activations and whitelisting the piwik.js file.