stelios

My previous teacher has been through a few different arts but admantly indicated towards Judo when asked similar questions.
I suppose that an Aikidoka would blend more easily with another martial art as long as there is sufficient flowing motion included.
From my experience, every single Karateka-boxer-kick-boxer-taekwondoka that visited our jojo and tried out aikido for alternative exercise had to quit very soon as they found that out flowing motion moves contradict what they had learned in the past (static defence/offence).
Shaolin kung-fu might be a nice alternative although as I have seen it in practise and I was not left everexcited.
If I had to look for something different I would go for Pagration (the ancient Greek combat martial art) although few teachers teach it nowadays.