I play exclusively on Peaceful difficulty. Lately I've been modding around the Spawner Core to compensate for the lack of mobs. I don't think it's worth releasing a mod-of-a-mod that only makes a few small changes, so I thought I'd run these ideas past you in case you think they have enough appeal to add to PNCR itself.

Spawner Core to Entity Loot

I wrote this as a Pressure Chamber recipe to maintain theme and function: Cores need pressure and Chambers collect items. Inserting a Core and an Air Grate into the Chamber produces the input items (they aren't consumed) and the loot of one of the Core's entities. The choice of an Air Grate is somewhat arbitrary, but I think it fits: you need something to catch the loot! Endlessly producing loot here requires a dedicated Chamber with some transporting and non-trivial filtering, not to mention endless pressure. This helps maintain the balance with conventional mob-grinding. (A third-party grinder machine with a Pressurized Spawner and some speed upgrades could do the same work faster.) Also, some of the lost sense of difficulty can be made up for with the new and fabulous option to alter required pressure according to the input. (My implementation sets the pressure requirement according to the health of the Core's strongest entity. A hearty entity like an Iron Golem could require a pressure that risks breaking the Chamber.)

Spawner Core to Melted Entity Fluid (Tinker's Construct)

Similar to the above, but replacing the Air Grate with a fluid-storing item such as a fluid tank. The Pressure Chamber "melts" an entity from the Core and inserts the result into the tank. The Core and tank are returned as output. Tinker's Construct recipes determine which fluid is produced. As with loot, cheaty-ness is balanced with the overhead of the setup complexity and pressure requirement. The Thermo Plant may be a better thematic fit here than the Chamber, melting the entity into the Plant's fluid tank. However, unlike the Chamber, the Plant is not currently coded to produce output specific to the input's NBT. It could also be argued that the Plant is too similar to a Tinker's machine for this purpose, or that the Plant makes things too easy since it requires less effort than the Chamber approach to melt continually. (It's still a reasonable option, though.)

Spawner Core as Dungeon (Chest) Loot

I haven't implemented this one yet, so I can't comment on how it plays. But one of the persistent problems I've had outside of Creative mode is a lack of variety among vanilla spawners. Even with some good dungeon mods to help, there are still plenty of mobs (and therefore loot items) that are only available to Peaceful players by Creative means. I think random Cores in dungeon loot (combined with the recipes above) would help with this, and would encourage the use of other Spawner Core features. I imagine the implementation to be modest, as a rare find with only a small portion of the Core filled with one or two random entities. Even heavily nerfed it would still be a QOL improvement.

Creative Spawner Core Factory

Make Cores without needing other machines. There's no obvious value in a Core Factory beyond testing other Spawner Core features. That said, I think it's easy to miss opportunities for Creative items. The Spawner Core Factory I've made enables adding non-living entities into the Core, which allows for wonders like this TNT fountain:

Let me know what you think.

Some interesting ideas here for sure, I'll have a think on them...