Generally the AI doesn't used mixed-level waves, but there might be some prior planets hanging around that might be mark I still. So if you killed their command station and their ships then came flooding out at you, then this would be useful in that context.
But I do have good news! Well, on two fronts:
1. The Ion Cannons also damage engines. So, even though they aren't going to be killing any higher-level ships, they will still be stalling them out, which is nice.
2. The tech level of the AI can be lowered! Just go kill some datacenters as part of some long-range raiding, and viola. You won't be able to keep their waves at Mark I forever, but you should be able to keep it lower for a good while, at least.