I don't know if you've ever had this issue, when you want to wear a jumper/cardigan/sweater but the sleeves on your abaya means that your arms look bulky and it can sometimes be uncomfortable.
Easy solution? Wear a sleeveless, t-shirt style or bandeau style maxi dress, which can be worn over a basic long sleeve top if you want/need arm coverage. Because of the sweater/jumper no one will know whether you are wearing an abaya or a maxi dress. You could even pair together a maxi skirt and long sleeve top (check out MangoWhirl's blog post on 3 ways to wear a black maxi skirt for inspiration and idea's).
Below are some outfit's that are inspired by the maxi dress and jumper combination =)
Bandeau style maxi dress and a cropped jumper:
Vest/sleeveless maxi dress and a cropped jumper:
Long sleeve t-shirt maxi dress with 3/4 sleeve jacket:
Just a note: If the maxi dress is made of a jersey fabric, make sure to get a larger size so that it doesn't stick to you (and thus doesn't show your body shape) =)