...Nothing builds a more competent Aikido practice than getting smacked/kicked in the face or being forced to tap out.
Why? Well Most Aikido Dojos I've seen have beginners who have no prior Martial Arts experience and they need to see and feel what a fight may "look like" including me... They also need to feel punches and kicks...Just my Opinion...Getting smacked in the face and still being able to execute a technique is a sign of competence not failure. And being able to execute a technique when faced with a competent Martial Artist while remaining true to the spirit of Aikido...That's Mastery.
We're encouraged to cross train in our style of Aikido so... No...That's one of the things I love about Shoji Nishio's Philosophy of Aikido... Aikido has to work as a Martial Art and unless you adapt and test it... It will atrophy and die.
Reading William Hazen's post, specifically, and this thread, in general, makes me feel better about
cross-training in Aikido.
Lat year, I was training only a few hours a week, but while surfing I had realized the the importance in be earnest about holistic training. "Where the mind is at" is key to catching a wave that can hurt and the the way to the mind is through the physical (here I'll refer to Bodhidharma's experience when training monks).
I hear the cops in Japan cross-train in Judo and Kendo.
One observation I have is that a beginner budo-ka will really benefit from focusing on one art and building a physical fitness base. Now, if you do BJJ often you will gain fitness just from class.