Our default taxonomy (POWO) shows this as a synonym of var. polyacantha. Are you wanting to propose a deviation from POWO for this name?

I would have to answer yes. However, as with most taxonomy, it is a judgement call. Var. schweriniana is a very distinctive little dwarf high elevation variety, easily distinguishable and stable within it's distribution area. Since it blends with other varieties (polyacantha, juniperiana, hystricina, rhodantha) at it's lower limits, it should be considered a variety as Backeberg placed it, and not as a distinct species. This variety is clearly not just made up of "stunted" plants as sometimes stated, but is a genetically determined elevational/regional variant, as shown by plants remaining dwarf when moved to a warmer climate. The name should not just be ignored by lumping it.

Coming up with literature based justifications is difficult with Opuntia, since the genus is a mess regardless of what source of information one turns to [particularly so on-line]. This is the case for a number of Opuntia names that have been ignored as if the plants don't exist. Descriptions of both of the following names have good discussions; this taxon is well-supported by the authors, and illustrations are included with both original descriptions. However, (inexplicably) the taxon is lumped as a synonym of either O. fragilis or O. polycantha var. polyacantha in many online databases, while in some recent literature it is lumped under O. polyacantha var. hystricina (but in the later case with discussion that it may deserve varietal recognition).

Here is the original description of O. schweriniana, which is the name of priority at both varietal and species rankings:
Opuntia schweriniana K.Schum., Monatsschrift für Kakteenkunde 9:148. 1899 https://www.biodiversitylibrary.org/item/49721#page/160/mode/1up
Type locality: Sapinero, Gunnison County, Colorado

Here is the citation for the first official placement of schweriniana at varietal ranking under Opuntia polyacantha:
Opuntia polyacantha var. schweriniana ( K.Schum. ) Backeb. Cactaceae (Backeberg) 1: 607. 1958
http://www.ipni.org/ipni/idPlantNameSearch.do?id=175451-2&back_page=%2Fipni%2FeditAdvPlantNameSearch.do%3Ffind_infragenus%3D%26find_isAPNIRecord%3Dtrue%26find_geoUnit%3D%26find_includePublicationAuthors%3Dtrue%26find_addedSince%3D%26find_family%3D%26find_genus%3Dopuntia%26find_sortByFamily%3Dtrue%26find_isGCIRecord%3Dtrue%26find_infrafamily%3D%26find_rankToReturn%3Dall%26find_publicationTitle%3D%26find_authorAbbrev%3D%26find_infraspecies%3Dschweriniana%26find_includeBasionymAuthors%3Dtrue%26find_modifiedSince%3D%26find_isIKRecord%3Dtrue%26find_species%3D%26output_format%3Dnormal

Here is the original description of O. heacockiae, which is a synonym:
Opuntia heacockiae Arp, Sida 10(3): 207 [corrected from 'heacockae'. 1984] https://www.jstor.org/stable/41966649?seq=1#page_scan_tab_contents
Type localtiy: w. side Trout Creek Pass, Chafee County, Colorado.

The name "Opuntia heacockiae" was a re-description of Opuntia schweriniana based on the false assumption (gleaned by the author secondhand from statements published by Lyman Benson) that the later name is a synonym of Opuntia fragilis. In point of fact the original illustration and type material of O. schwerinaina show it and O. heacockiae to be the same name, and this has been pointed out and discussed numerous times in numerous forums. Thus, the name O. heacockiae is a later synonym, and a redescription of the same plant. Perhaps it is invalid, because published as a superfluous replacement name. [Determination would be up to judgement by a panel of the International Commision on Botanical Nomenclature, but is not important, as it has no affect on the proper name to be used.]

There is a discussion of varieties of Opuntia polyacantha online here:
https://www.opuntiads.com/opuntia-polyacantha/#unique-identifier6

I see this taxon has been added, but with no pertinent taxonomic framework deviation. should this flag be closed and var. schweriniana itself flagged, or the discussion continue here for documenting the deviation etc.?