KEP-4438: add missing sections

Signed-off-by: Matthias Bertschy <[email protected]>

Author: matthyx

keps/sig-node/4438-container-restart-termination/README.md

@@ -277,6 +277,14 @@ How will UX be reviewed, and by whom?
 Consider including folks who also work outside the SIG or subproject.
 -->
 
+The main risk of this proposal is that the lifecycle of sidecar containers will be changed, which could
+potentially break existing behavior. To mitigate this risk, we will introduce several e2e tests
+and peer review to ensure that the changes are safe.
+
+There is no security impact of this proposal.
+
+The UX impact of this proposal is minimal, as it adds an expected behavior to the lifecycle of sidecar containers.
+
 ## Design Details
 
 <!--
@@ -902,6 +910,11 @@ Major milestones might include:
 Why should this KEP _not_ be implemented?
 -->
 
+The main drawback of this KEP is that it introduces a new feature gate for the sidecars,
+which can be confusing for users. However, we believe that the current behavior of sidecar containers
+is already useful and that the restart during Pod termination feature is not critical for many use cases.
+This is why this feature is introduced as a separate feature gate, so that KEP-753 can reach GA faster.
+
 ## Alternatives
 
 <!--
@@ -910,6 +923,11 @@ not need to be as detailed as the proposal, but should include enough
 information to express the idea and why it was not acceptable.
 -->
 
+The alternative would be to introduce KEP-753 with the restart during Pod termination feature.
+However, this would have required a significant refactoring of the kubelet
+and the Pod lifecycle, which would introduce a risk of disruption to users. This is why we decided to
+introduce a separate feature gate for the sidecar containers feature.
+
 ## Infrastructure Needed (Optional)
 
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