I've already mentioned elsewhere that I approve of the idea of being able to re-create clusters (though making it a synth to do so requires reworking the synthesis system to allow for recipes with more than 8 ingredients as the synth code manually unstacks things at some point).

Stacking ores (99?) and logs (12) is also a good idea. (For that matter, stacking juices would be nice, especially in combination with allowing HQed juice recipes to produce more than one juice. Yes, I know you can do that with synergy. The only excuse for not doing it on normal cooking is that normal synths don't produce more than one unstackable item, which making juice stackable solves.)

Portafurnaces: I suspect the issue is that the code is derived from that of the Chocobo Whistle. (I don't know if this would make it harder to fix, or if it's a matter of just disabling the zone check.)