First thing would be to track down the actual factual Outpost that civs can build and its animfile. If you’re hunting for something the easiest way is usually going to be to get the protoy.xml out of Data.bar as well as the stringtabley.xml as you can then search for the unit or building and see what its exact animfile location is, using the stringtabley to cross-reference the in-game name or descriptions to get a string number to search for it in the proroy if needed.
Some protoy names will differ like Salteador is “deEmboscador” which is why cross-referencing can be vital, but this one is going to be pretty easy to find as its protoy name is just “Outpost.” Once you find the animfile for it (buildings\outpost\outpost.xml) extract it out of ArtBuildings.bar and remember to convert it to XML. I think you did find the other one at buildings\spc\tower\tower.xml so extract that into XML as well.
Some animation files are more complex than others and feature Submodel sections with the model and animations for that model contained within the Submodel tags, with a final Component section where you dictate which submodel goes where and with what. Below is the Outpost component section. You can see it uses Tech Logic for “none” meaning how it looks with no techs, and then the two Outpost upgrade techs. The “none” section uses additional Logic for Culture (the building set defined in civs.xml) which says if you have none or no special culture defined then it uses those submodels, but if you have africaeast culture it uses those submodels instead. These kind of logic tags are how you can set things up to look different for specific cultures, civs, or techs.
<component>outpost
<logic type="Tech">
<none>
<logic type="Culture">
<none>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="sub_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="sub_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="Outpost lvl1_con2"/>
</p66>
<p100>
<submodelref ref="Outpost lvl1"/>
</p100>
</logic>
</none>
<africaeast>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="sub_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="sub_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="eth_tower_con"/>
</p66>
<p100>
<submodelref ref="eth_towerA"/>
</p100>
</logic>
</africaeast>
</logic>
</none>
<frontieroutpost>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="sub_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="sub_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="Outpost lvl2_con2"/>
</p66>
<p100>
<submodelref ref="Outpost lvl2"/>
</p100>
</logic>
</frontieroutpost>
<fortifiedoutpost>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="sub_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="sub_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="Outpost lvl3_con2"/>
</p66>
<p100>
<submodelref ref="Outpost lvl3"/>
</p100>
</logic>
</fortifiedoutpost>
</logic>
</component>
In this case, the Tower.xml already is using submodels, so it’s a relatively simple task of carefully copy+pasting the submodels into the Outpost.xml as their own submodel sections. You’ll need to rename the Tower’s two Sub_construction submodels as those exist already in Outpost.xml, and remember what you change it to because you’ll need to add it at the bottom.
Those were the easy steps, now comes the harder part. Let’s say you only want the Tower to show up for the final upgrade aka fortifiedoutpost tech, you could add another logic type=“Tech” tag inside there, copy the existing look under a none tag so it looks like that for everyone else, then add deage0italians and deage0maltese sections using the Tower submodels names you moved over. If you want it to always look like that then you do the same thing for the two other main tech logics sections (frontieroutpost and none), remember that none is already coded using the Culture logic so you’d add a mediterranean culture tag then add a tech logic within that with none for the default look and then sections for the age0s for Italy and Malta.
<fortifiedoutpost>
<logic type="Tech">
<none>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="sub_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="sub_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="Outpost lvl3_con2"/>
</p66>
<p100>
<submodelref ref="Outpost lvl3"/>
</p100>
</logic>
</none>
<deage0italians>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="spctower_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="spctower_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="tower_con"/>
</p66>
<p100>
<submodelref ref="tower"/>
</p100>
</logic>
</deage0italians>
<deage0maltese>
<logic type="BuildingCompletion">
<p0>
<submodelref ref="spctower_construction_stage_01"/>
</p0>
<p33>
<submodelref ref="spctower_construction_stage_02"/>
</p33>
<p66>
<submodelref ref="tower_con"/>
</p66>
<p100>
<submodelref ref="tower"/>
</p100>
</logic>
</deage0maltese>
</logic>
</fortifiedoutpost>