Hypothetical
There have been discussions between the members of the polyphasic community about unexplored exotic sleep mechanisms or schedules, which have only a couple of attempts if any. Worth mentioning, it's advised not to attempt them unless you're an experienced polyphasic sleeper.
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 inserting light sleep at the exact time of daily waking up, which means it's likely possible to start getting refreshing/natural wakes from pronaps even on reducing schedules even outside of 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 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.
