Hl7 FHIR Extensions: nesting, slicing, ids and discriminators - hl7-fhir

Question

Due to a (somehow) special requirement to store data alongside a FHIR resource, I am looking for the cleanest way to extend it to maintain such extra data, which is basically dynamic key-value lists.
On the one hand I have something like the following, with 0..* sets of key-value, that I have tried to store nesting three extensions (adjusting the context by level) being the last a single limitation to the accepted types (string/integer), although it does not allow me to repeat ids, anyway I am getting around it using prefixes XD.
"n-lists-of-key-value": [
{
"list1-key1": "list1-value1",
"list1-key2": "list1-value1",
"list1-key3": "list1-value1"
},
{
"list2-key1": "list2-value1",
"list2-key2": "list2-value2"
}
]
becomes:
···,
"extension": [ {
"id": "n-lists-of-key-value",
"url": "http://x.org/fhir/Extension/NListOfKeyValueExtension",
"extension": [ {
"id": "list_1",
"url": "http://x.org/fhir/Extension/ListKeyValueExtension,
"extension": [ {
"id": "list1-key1",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list1-value1"
}, {
"id": "list1-key2",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list1-value1"
}, {
"id": "list1-key3",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list1-value1"
} ]
}, {
"id": "list_2",
"url": "http://x.org/fhir/Extension/ListKeyValueExtension,
"extension": [ {
"id": "list2-key1",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list2-value1"
}, {
"id": "list2-key2",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list2-value2"
} ]
} ]
} ],
But on the other hand I have this, which is what I find most difficult to model, because trying to reuse the extension definitions I run into (conceptual?) difficulties with slicing and the use of the discriminators, failing to get past the error "Element matches more than one slice".
"my-3-fixed-named-sets": {
"fixed-named-set1": {
"list1-key1": "list1-value1",
"list1-key2": "list1-value2",
"list1-key3": "list1-value3"
},
"fixed-named-set2": {
"list2-key1": "list2-value1",
"list2-key2": "list2-value2"
},
"fixed-named-set3": {
"list2-key1": "list2-value1",
"list2-key2": "list2-value2"
}
}
becomes:
···,
"extension": [ {
"id": "my-3-fixed-named-sets",
"url": "http://x.org/fhir/Extension/NListOfKeyValueExtension",
"extension": [ {
"id": "fixed-named-set1",
"url": "http://x.org/fhir/Extension/ListKeyValueExtension,
"extension": [ {
"id": "list1-key1",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list1-value1"
}, {
"id": "list1-key2",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list1-value2"
}, {
"id": "list1-key3",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list1-value3"
} ]
}, {
"id": "fixed-named-set2",
"url": "http://x.org/fhir/Extension/ListKeyValueExtension,
"extension": [ {
"id": "list2-key1",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list2-value1"
}, {
"id": "list2-key2",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list2-value2"
} ],
}, {
"id": "fixed-named-set3",
"url": "http://x.org/fhir/Extension/ListKeyValueExtension,
"extension": [ {
"id": "list2-key1",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list2-value1"
}, {
"id": "list2-key3",
"url": "http://x.org/fhir/Extension/KeyValueExtension,
"valueString": "list2-value3"
} ]
} ]
} ],
I am aware that by indiscriminately including new extensions with different names/urls, I can end up ingesting all the data, but I suspect that there is a much cleaner way and that I am failing in , probably, the way to include an extra condition into the discriminator (https://hl7.org/fhir/profiling.html#slicing), so that I could point to the proper slide? or de fact of extending extensions or extending value[x] slices?
"discriminator": [
{
"type": "value",
"path": "url"
},
{ "???": "??Extension.value.slideName??
···
Then my specific question would be... can I slice the value[x] of the extension of a specific profile, and which in turn make them extensions? this lasy is to get having n key value lists
Any comment is very welcome :)