I think it's fine to include low-hanging fruit outright. That is, if it takes a comparable effort and number of code lines to implement an O(n²) solution and O(n) solution, there's no reason not to pick the better of the two.

I don't think that plunging into a massive rewrite without some profiling / evaluation is a good idea. What evidence do you have that the new approach will be faster? Do you have a testing prototype, or someone else's experience with the 3rd party engine you mention? Can you spend a day or two to make this clear, and get some hard numbers?

Is there any hard evidence that the piece you're going to optimize is an actual bottleneck? Usually ~10% of code spends ~90% of cycles; if the rest ~90% of code becomes twice as slow, nobody would notice. Make sure you're optimizing an actual hotspot.

I think it's fine to include low-hanging fruit outright. That is, if it takes a comparable effort and number of code lines to implement an O(n²) solution and an O(n) solution, there's no reason not to pick the better of the two.

I don't think that plunging into a massive rewrite without some profiling / evaluation is a good idea. What evidence do you have that the new approach will be faster? Do you have a testing prototype, or someone else's experience with the 3rd party engine you mention? Can you spend a day or two to make this clear, and get some hard numbers?

Is there any hard evidence that the piece you're going to optimize is an actual bottleneck? Usually ~10% of code spends ~90% of cycles; if the rest ~90% of code became twice as slow, nobody would notice. Make sure you're optimizing an actual hotspot.