Hypothetical
There have been discussions between the members of the polyphasic community about unexplored exotic sleep mechanisms and potential schedules, which have few to none attempts so far.
Longer naps
Extended naps, sometimes referred to as pronaps, usually have a length of 40-45 minutes. They were suggested first by Jelte to be used during the dawn hours, after needed SWS is met and REM is prioritized by the brain. It turned out to be successful, allowing to get more REM/LNREM, and is used quite often. Longer naps also proved to be successful on non-reducing biphasic schedules such as BiphasicX, having refreshing natural wakes. Other than that, pronaps aren't recommended on the reducing schedules, since they have mid-cycle wakes during SWS, which is not refreshing naturally and leads to sleep inertia or sometimes zombie-mode following by oversleeps. However, it was suggested that such mechanism as wake time programming might cause the adaptation of brain to insertion light sleep at the end of the sleep blocks, which means it's likely possible to start getting refreshing/natural wakes from pronaps even on reducing schedules and even outside of the REM peak. There is a couple of examples of this mechanism, which were suggested.
Metaman
Being a famous polyphasic schedule, Uberman is considered not doable for most people, since the total sleep time is much lower than the average bare minimum of sleep needed. Metaman was suggested by Sekvanto with the purpose of having a similar to Uberman mechanism, at the same time being theoretically doable for people with a bit lower than average sleep requirements (~7h monophasic baseline or shorter vital stages needs), therefore has a prefix "Meta-" opposing "Uber-" and "Every-". It has six 40-minute naps, equidistantly placed throughout the day, with a total sleep time of 4h. If confirmed, this schedule will belong to a new Pronap-only category. Worth mentioning, even though the total sleep time theoretically allows to get the needed duration of vital sleep stages, it is unlikely that the naps can be compressed much enough for having long uninterrupted chunks of SWS (30m or more) needed for the glymphatic system to finish a session of cleaning brain waste, so similarly to nap-only schedules, no conclusion about the health implications of waste products in the brain on this schedule can't be made yet.
Metamaxion
Similarly to Metaman, this schedule is the extended version of Dymaxion, another nap-only schedule with a low total sleep time. Metamaxion was suggested by Zandimna as an improved version of Metaman with less blocks of sleep needed, which is easier to schedule around the day. It has four 50-minute naps, equidistantly placed throughout the day. This length is on the borderline which divides cores from naps, so sleeps can be shortened to 45 minutes to ensure they are definitely naps. Nevertheless, the total sleep time on Metamaxion is less than 4 hours for both options, so one needs a bit lower than average sleep requirements for the adaptation. Longer naps duration means that it's more likely to reach the needed sleep compression for having long enough SWS episodes for the efficiency of the glymphatic system, however this is still extremely difficult for an average person, so the same question as about Metaman remains on this schedule too.
SPAMAYL-40
Basically has same characteristics as a regular SPAMAYL, except the naps are longer on this one. The amount of naps needed also can be decreased compared to SPAMAYL with shorter naps, which makes this easier to schedule around the day. Also, similarly to Metaman and Metamaxion, SPAMAYL-40 is a bit more double for regular people. This schedule was suggested by many people, partially done by Sporky once, who mixed it with shorter naps too though. Longer naps had an architecture of mini-cores, often containing both SWS or REM or one of this stage being dominant. Sporky's average sleep cycle is close to 90 minutes on monophasic sleep, which either was compressed so much or used a wake time programming method to insert some light sleep at the end of the naps, which made waking up easier. Similarly to the above mentioned schedules, SPAMAYL-40 doesn't allow for long uninterrupted SWS episodes, which likely is unhealthy for the glymphatic system process.
Modified schedules with the nap extension
Taking any regular schedule with extended nap(-s), a new schedule of this category will be the result. An example includes DC1-modified on a picture near this paragraph, which has a 40-minute nap outside of the REM peak. The mechanism of this likely differs from the pronap-only schedules above, since the total sleep time is much higher and the compression levels are much lower. Also all needed SWS should easily be placed in the cores, which possibly will allow longer naps have little-to-no SWS, thus making them more refreshing initially. It is unclear if the wake time programming will be applicable in this case too, but this is worth experimenting. Longer naps on the regular polyphasic schedules might also compensate for a bit shortened cores (e.g. a DC1 variant with 3h + 1.5h cores, or a E2 variant with a 4h core).
Short gaps
According to this research, the polyphasic sleep community has an established recommendation to leave at least 1.5h gaps between two blocks of sleep, preferably even longer (about 3 hours) to ensure brain doesn't count them as one interrupted block of sleep, decreasing their quality. It was found in the study that frequent awakenings followed by immediate returning back to sleep decrease sleep quality, leading to a higher percentage of light sleep. A known Zoidberg attempt has proven this statement, after two sleepers couldn't adapt to the schedule because of much lower sleep quality. But recently a new idea was suggested by some members of the polyphasic community. In fact, it's possible that the main reason of the reduced sleep quality on schedules with short gaps were not the gaps by themselves, but rather SWS interruption, or mid-cycle wakes in general. Therefore, a new mechanism was suggested - full cores with a short gap (30-60 minutes) in between. This makes getting long uninterrupted chunks of SWS possible, and likely will lead to a normal sleep structure (similar to a one with longer gaps between cores). Also it might be possible to have a few REM naps close to each other during the dawn hours, with each of them having a high quality.
