Follow up on my last post.
I did the same workarround a few days after I posted this (just couldn't wait) 
1. Upgrade of my 5 esxi 5.1 hosts to newest patch.
2. Downloaded the esxi image (VMware-ESXI-5.5.0-1746974-HP-5.72A.3-Jun2014.iso) from VMware download.
3. Uploaded the esxi image in vCenter and created baseline in Update Manager.
4. Scan all hosts (Cluster), so status is non-compliant instead of Incompatible.
5. Put the host in Maintenance mode.
6. Remediated host with the attached baseline for esxi image (had a ILO console to the host while upgrading, because when upgrade is finished you'll have to press ENTER to confirm the last reboot)
7. When host is up and available in vCenter, then scan for new patches.
8. 20 updates (for esxi 5.5) were found and remediated them.
My environment is now up and running the latest version (VMware ESXi, 5.5.0, 1892794), hope I save you guys some time.