Lewis, thank you for the fast reply, which is clear.
We have two FREESCOs in use, these are 0.4.2 and 0.4.4 (and we have FRRESCO 0.4.5 on a development machine). The 0.4.2 machine is on a dynamic range and would most benefit from being able to use https for a dynamic ip update. (The 0.4.2 system is also used for fallback to 3G and, due to 3G line-of-sight needs to the cell tower, is in a relatively inaccessible position in the building, and difficult to update the OS which is why it is still at 0.4.2, despite the subsequent FREESCO releases.) Package updates are easy, though, with the package menu system served over SSH. So we'll proceed with wget and openssl.
DynDNS service is continuing until the end of April (I think), so there's some time yet.
Look forward to trying this out.