44 inch external door opening

I am looking to replace the entry door to my garage. The current door is for 2x4 walls so it isn't deep enough for 2x6 walls. Also the block rough opening is 44" wide and the door is a 36" door. The gaps are filled with OSB and it just doesn't look good (see pics). I found a few doors that would be a tight fit. They call for a 44.5 inch rough opening. Below are a few ideas I was tossing around, I'd like to hear your thoughts on this. I'm also curious if 44" is common or what you think they previous owner may have been planning to do with it. The garage was built by the homeowner and the garage doors have the same issue so this may just be inexperience. I'm thinking the only options for the garage doors would be wider trim.

1. Stick with a standard 36 inch door and cover the OSB with wide trim. I don't care for this idea because the trim wouldn't match the rest of the house.
2. Fill the extra space with concrete or block to remove the OSB. This would probably stand out against the existing block, but at least it would hold up to the weather.
3. Have a custom door made or try one of the doors that require a 44.5 inch opening. I'm leaning towards this option.