hi facugo,
The only requirement for running IAP of different models in the same cluster is that all need to have the same software version. If the IAP's have access to the internet or Airwave, a new AP, joining the cluster, will update to the software version, already running in the cluster (given the fact, the new IAP supports the software version, running in the cluster).
The IAP103 supports software version 6.5.4.12. The 205 do as well. So this would be my recommended software version when mixing those two IAP's.