Rhymes on -omen and -open
These people: http://www.rijm.nu/rijmen/rijmen.php?woord=weggenomen seem to agree with me, at least.
These words are indeed stressed on the same (penultimate) syllable. Secondary stress is also stress. Would you also say that beestenbende does not rhyme with rende or that English lever action [ˈlɛvəɹˌækʃən] does not rhyme with fraction [ˈfrækʃən] or that Icelandic Ganamaður [ˈkaːnaˌmaːðʏr] does not rhyme with daður [ˈtaːðʏr] ??
If you want evidence from actual Dutch poetry, a quick look through the Oud-katholiek gezangboek (2006) will yield such rhymes as leven — uitgedreven, heerlijkheid — zijt, koningsfeest — Geest (exactly of the type I described), and also rhymes with secondary stress on both sides: honderdvout — lijfsbehoud.
No, they are perfect rhymes, due to having identical pronunciation from a point of stress to the end, although rhymes where the two words share primary stress may be considered stronger. An imperfect rhyme (half rhyme) has an unstressed vs. stressed syllable (e.g. undid — liquid) or non-identical phones in the coda (e.g. glad — bed). In your own guide to Dutch rhymes (Rhymes:Dutch), you say: “Two words are rhymes if they are stressed on the same syllable, counting from the end of the words, and are pronounced identically from the vowel in their stressed syllable to the end, but have different consonants immediately before that vowel.” This is taken directly from User:Paul G in Rhymes:English ( https://en.wiktionary.org/w/index.php?title=Rhymes:English&oldid=123029 ), and these have been taken as definitive guidelines for rhymes on Wiktionary for a long time. The words opgenomen, beestenbende, lever action, and Ganamaður are all stressed on the penultimate syllable, even if they are also stressed on the first syllable, and if we compare them to the words komen, rende, fraction, and daður, respectively, they do rhyme by this definition. That there is also stress earlier in the word has no bearing, whether it be primary or secondary stress – these guidelines do not distinguish between the two, but name only stress, and you must admit that secondary stress is stress. Paul G's example of non-rhymes due to different stress are undid [ʌnˈdɪd] and liquid [ˈlɪkwɪd], the latter of which is completely unstressed on the final syllable, which therefore cannot make a rhyme with the [ˈdɪd] of undid. This counterexample given in the guidelines therefore does not support your position, as it pertains to an altogether different case. Certainly the rhyme guidelines need expansion; they should have more examples and examine in more detail different stress patterns. Tone should also be discussed, and Wiktionary:Rhymes should mention considerations for different languages and offer general guidelines, etc.
Technical definitions notwithstanding, it can be inferred from the wider context of Paul G's guidelines that he considers words to be “stressed” in only one place. Excluding rhymes on secondary stress has also been his practice (and yours, as well as that of several other editors) when editing rhyme pages. You cannot, however, maintain that there is some broad Wiktionary consensus unambiguously on the side of not allowing secondary stress to count toward a rhyme. The rhyme guidelines are not clear enough for that, and no formal policy has been enacted on the matter, or on rhyme pages at all. Several other users have also been adding rhymes of this type to rhyme pages such as Rhymes:English/eɪt, Rhymes:English/iːn, etc., some of which have been reverted, but many of which still stand.
I also think it is important to note that when words are examined in context, it is very difficult to make a clear distinction between primary (strong) and secondary (weak) stress for this purpose. Words which only have one stressed syllable, e.g. houden, have varying degrees of stress depending on the surrounding words, and when e.g. preceded by another such word with stronger stress, the (primary) stress of the following a word can be identical to secondary stress in a four-syllable word: houden in a sentence ending in “van mannen houden” [vɑn ˈmɑnə(n) ˌɦɑu̯də(n)] is basically the same as in a word like tegenhouden [ˈteːɣənˌɦɑu̯də(n)], and would then not (by your argument) be a perfect rhyme with e.g. gouden, which would likely receive heavier stress in sentence-final position. Similarly, normally weak stress can become heavier in different circumstances, such as due to emphasis (e.g. to contrast with another word element). In poetry, the meter also changes the weight of the stress, and in poetry both in Dutch and English, there is a lot of indiscriminate use of primary and secondary stress. Since poetry is the main place we find rhymes in actual usage, and Wiktionary is based primarily on attestation, we cannot ignore this fact.
Due to their widespread use, I think it is obvious that these rhymes have value for Wiktionary, so they must be put somewhere. As it stands, rhymes are organised by syllable core (stressed vowel) and coda. Under this system, there is no other place for them but on the same pages as the other rhymes. I think it would be acceptable to place them among the other rhymes, making no distinction. This make it easier for casual editors to place words correctly on the rhyme pages and reduces maintenance, and also makes dealing with words where there are variations on the placement of primary stress. I myself have long included such rhymes in this way for Icelandic, and have never considered that to be a problem. Of course, nearly all Icelandic words have their primary stress on the first syllable, so, for Icelandic, rhymes of this type are usually all the rhymes on the page with more syllables than the rhyming part. There is therefore little need to distinguish them from the others for Icelandic, but I can see that many would want such a distinction for other languages, such as Dutch and English. I would therefore happily support making such a distinction, especially since several editors here and some authorities on rhymes do. This could be achieved e.g. by a separate header for rhymes on non-primary stress on the rhyme page. In any case, we clearly need to have a broader discussion on rhymes here on Wiktionary and come up with more comprehensive guidelines.