Ha, there's plenty! Coming up with potentially interesting compounds is not that difficult if you're following the current research and if you've tried a good variety of related compounds. Coming up with an economically viable synthesis method which then actually works is another thing though.
In terms of ACH's I wanna see some more PCsBu analogs like 3-Cl-PCsBu (I love 3-Cl-PCP) or 3-Me-PCsBu (3-Me for full on hedonism) because 3-MeO-PCsBu was a unique experience and highly selective for mania without really inducing physical dissociation (
you can read about it here). Putting a carbonyl on the 2-position of the cyclohexane ring could also be interesting and then resolving the different stereoisomers. Then shifting the carbon of the sec-butyl to an iso-butyl on the amine also sounds like it could be worth exploring.
In terms of PEA's I'd love to see 2C-SF5 (4-pentafluorosulfanyl) being made but the synthesis would be extremely expensive and not really worth it. The SF5-group has very strong electron-withdrawing effects (stronger than CF3) and the high polarity/lipophilicity in the 4-position could make for a very potent 2C compound. Steric bulk might make it a bit less potent than one would expect but the size should definitely be tolerated for decent activity. Then DO*, NBOH, NBOMe, NBI, and the other analog shenanigans.
Would love to see some tetrahydroisoquinoline analogs of the common 2C compounds (not that I think they would be particularily psychedelic), some chromane derivatives of the common 2C compounds (Tarik Peterson prepared the chromane derivative of 2C-D iirc but hasn't tried it), some more 4-R-2,5-dimethoxyphenylpiperidines, and so on and so forth.
Unlimited hypothetical compounds like I said, but the actual viability of creating them is another story.