Are transactions still tamper-proof if blocks are hashed without nonces? If an alt were to forgo difficulty and timed release of new supply by removing the nonce from blocks therefore the whole difficulty/target system, is hashing without nonces still providing the same blockchain anti-tampering security?

If not, how could the blockchain's integrity be maintained without hashing difficulty?

As I understand it, blocks have nonces to satisfy difficulty so that the hashing process is slowed for the purposes of controlling the rate new crypto supply is produced.

Please assume that supply will be produced through a multiplier as described here instead of as a reward for mining.  In this case, block generation doesn't need to be slowed for the purposes of crypto supply inflation, but the blockchain does need to be made tamper-proof.

Is it correct that simply hashing in particular ways make the transactions tamper-proof, or is noncing a hash also necessary?
Ripple is an example that works without proof of work nor proof of stake (so no nonce needed). This mechanism is more vulnerable to sybil attacks, so it needs strong peer identity knowledge (but not trust!) to be secure. See https://ripple.com/wiki/Consensus.