This. While I only have Lydia right now, she seems to very effectively swap between bow and sword. Now if only I could get her to last more than 5 seconds in a fight before she falls over until the fight ends....
Well, I don't know what Lydia is like, but I just checked the follower I've got following me right now instead of Lydia, Faendel, and his health is only at 92, whereas mine is at 130. You might open up the console, click on Lyida and do ModAV health somenumber you think is reasonable. You can check it first with GetAv Health and then decide. I added 40 to him to get him up with me. I assume he'll level with me, but maybe they don't? I'll check him again later on. I've only just picked him up and we've only gone through one fight together and he was fine so I haven't gotten a chance to see how puny he will be.