I looked up all the flanking cards in Visions. They all depict creatures on horses. So, I thought it'd be best to keep this person with flanking. Because this is just a guy on a horse, I didn't see simply taking away haste and making it bigger as something that makes sense. Having 3 power or 3 toughness, especially when having flanking, was just out of the question. But I couldn't make it a 1/1, either. That also didn't feel right for a guy on a horse. 2/1 feels more red than 1/2. So, I either had to adjust this card to be a 2/1 or come up with an effect that replaces haste and be able to pursue 2/2 in addition to 2/1 for stats.
Before I continued, I wondered whether 1 toughness made sense for a person on a horse. So, I did a search on red Knights. Yep, Defender of Chaos is proof that this is something that can make sense.
This is a common card, so there's not much wiggle room with what kind of additional effects I can give this creature. First strike was my next choice, but combined with flanking, that's pretty powerful. Besides, there's already a red flanking creature that has an activated ability to give itself first strike.
Then I looked at the flavor text. ..."never stop." AHA! The red drawback of "attacks each turn if able," was then added. Red can get a 2/1 for 1R at common, and flanking was a bonus, so the "attacks each turn if able" drawback balances out the upside.