didn't know about hardware/software decoder thing. will check it.
btw i found a site with 576p re-encodes. file sizes are also less than 100mb :)
sorry for bothering you.

As far as I know, placing links on nyaa's pages is rather hard.

Although not solving your issue, I might point out that if your phone is decoding video via a hardware decoder, the resolution won't affect battery usage (in any meaningful way at least).
If you're using a software decoder, well, only more recent phones actually have the CPU power to do such a thing reasonably, and these all have hardware decoders.

You might find that reducing resolution doesn't really reduce sizes that much. Though you could probably shave most episodes down to around 100-150MB at 576p with not too much quality loss if you tried.

If you're happy with asking a server to do it, why not try asking others to do it instead?

I suppose so, just the question somewhat is... perhaps it's more relevant to comment at the source (ie Nyaa)?
Other thing is how to display the link, since skipped stuff go directly to source. (actually, it's already possible to comment on these, if you can figure out the URL to them)

DeadFish is re-encode group but file sizes are still 200MB+ & they only do 720p which becomes storage issue in mobile devices & 720p drains batt. fast. DeadFish is also probably using some dedi server.

On Request re-encode might be better option,
so users will select video resolution 480/576 & click request button & Server will add it to encode queue
mp4 format is easily supported by mobile devices as long as its 8-bit & Quality is lot better than old Xvid avi format.

The main problem with this is that it requires a dedicated server with a fairly beefy CPU - not cheap. Other issues would include the fact that anime encoders tend to be rather exotic in their choice of formats they encode into, meaning that an automatic encode process could be difficult. Filtering out duplicates could be problematic too.

So it's not planned, but some groups like DeadFish seem to be doing re-encodes anyway...?