What would be the implications of limiting Bitcoin transactions to fifty inputs? One of the issues of increasing the blocksize is the possibility of creating attackblocks which would take significantly longer to parse than the common block. The mechanism to do so is by creating a transaction that fills the complete block exploiting the quadratic cost of verifying input scripts.

Bitcoin Classic proposed to limit the number of sigops per block. It seems to me that limiting the number of inputs to be used in one transaction would incentivize reduction of a wallet's UTXO footprint.

Has limiting the number of inputs been discussed as a potential solution? What would be the upsides and downsides of such a change?
The main concern with sigops is the quadratic behavior of the pre-segwit signature hash.  I believe specially constructed transactions with lots of OP_CHECKSIGS but few inputs would be similarly bad as transaction with many inputs.

Having additional limits also makes life a little harder for anyone working with the system; e.g. you have to be under 100k, AND under 50 inputs.

Ultimately the best solution is to avoid quadratic behavior like the new signature hashing in Bitcoin did.