In the installers install-tree allow a possibility to disable selecting a node, but child nodes could still be selected as normal. E.g. define this in components package.xml something like:
<AllowSelection>false</AllowSelection> <!-- deafult is True-->
The rationale behind this:
Especially for embedded offering, people often just select the top level item in install tree thus they end up installing all possible embedded packages ~10-20G accidentally. This causes installation cancellations and unnecessary network traffic.
If we could disable clicking on e.g. qt.embedded.b2qt  check box the user would need to actually "think" what he needs to install under the sub-components.