Why do you think, that it complicates testing? Testnets should produce no new coins at all, and allow just pegging things in, testing them, and then destroying UTXOs during peg-out.

Imagine, how testing could look like, if you could just import some mainnet transaction into testnet (for example by revealing some SPV proof), do some test transactions, and then all of it could be disposed, by burning UTXOs.

The only reason, why any non-zero amounts are needed, is to pay for fees. But there are more ways to make the network spam-resistant. For example: if all amounts are zero, then Proof of Work can still decide, which transactions are included, and which are excluded, when mempools are full.

Think about it: testnet coins are worthless, right? So maybe that should be at least reflected properly, by setting amounts in satoshis into zero?