Well, please don't misunderstand me, but why do you have to lift weights. Aikido is almost impossible to master in one's life time, so why don't you practice instead of wasting your time doing weights. I myself practice 6 days a week, sometimes 7. During public holidays, I do bokken suburi and jo kata at home. If you think your arms need strengthening, why don't you try doing 1000 suburi ichi with your bokken, and let me know the result
If weight lifting is your hobby, then it's a different story, but if you wanna do it to get better in aikido, well, there is only one way: practice aikido, as many hours a day as you can. Our shihans and teachers had to practice over 7 hours a day to reach their level of efficiency and they're still not perfect.
Just my opinion.