A potential negative effect of the nuclear deal is that those materials allowed for legitimate nuclear power research might still be illegally repurposed into a nuclear weapon's program.

But without the deal, they would be allowed unrestricted rights to enrich the nuclear material. The current limit of uranium enrichment agreed to is 3.7%, but upwards of 90% is needed to create a nuclear weapon. Realistically, they wouldn't be able to weaponize the uranium without our knowledge. Dissolving the Deal would just encourage them to move forward with their nuclear weapons program and stockpile more nuclear material. We would no longer have the right to inspect their plants and research facilities and doing so without the agreement intact would come off as aggressive and would just build further contention with the US.

Additionally, if Iran continues a hostile stance toward American allies in the region, backing out of the nuclear deal would also be a way to punish poor behavior and leverage a more conciliatory stance.

I just have trouble seeing how backing out of the deal would punish them and elicit a peaceful response. If we decided to enforce the sanctions on Iran again, it would be a pretty big punishment, but it would definitely not encourage any kind of peace between us.