The huge invalid UTXO will be the last in the exit queue, so the contract will be emptied out before that exit is processed?
Napkin math ahead:
Operator submits exit. Each block can handle 9 million gas. Let’s say that a new block gets mined every 15 seconds. There are 40320 blocks per week. Let’s also consider that the exit period is a week. Each exit let’s say costs 100k gas.
40.320 * 9.000.000 / 100.000 = 3.628.800 UTXO exits that can fit in that period, which is the maximum we can handle with the above things in mind
I’d imagine that having 3.6 million UTXOs being exited for a large plasma chain to be reasonable. Also consider that you do not have only exit transactions in the above said gas capacity, you may have any other challenge related tx’s with respect to the plasma contract in question, let alone any other on-chain gas costly ones. So yes, I do believe that in non-NFT Plasma designs are much necessary