Attacks with live weapons and you are worried about uke being able to take the ukemi? Its just my opinion, but most sincere attacks with a marker will probably show that nage would be bleeding in a real situation.
We started off slow and built up speed as we learned to react correctly. The sincerity and intention were always present! (Ukemi is more challenging as you have to avoid landing on or dropping the blade..
Just as you don't start out doing ikkyo or shihonage at full speed as a beginner, you don't start doing live weapons training at full speed either
A thought for the OP - maybe with our modern risk-averse and litigatious society, many Aikido dojo have been required to water down the martial aspects in order to attract sufficent students to survive, or to comply with insurance requirements?