Thing is, how does one get the needed views and subs to get partnered.... without making lets plays? It would make the channel look weird if you got tons of views and subs with say... comedy skits.. and then abandon that once you have enough to get partnered and start doing lets plays.
It doesnt really make your channel look weird, but it can alienate part of your original sub base, I was a CoD commentator (yes that stale rubbish) for a couple of years before switching to Lets Plays in november of 2011, around that time I had 3k subs and just gained my partnership so kinda the scenario you said though comedy -> lets plays is more of a jump than one kind of game commentary to another.
A Year later im sitting at 10k subs, I dropped a fair bit of the previous CoD subbase of course so it was a rough transition to start with and the split base may not have appreciated it, but in the month I finished CoD I was making 22k views a month, in the most recent complete month (january) I had 613k views, (not the biggest gains I know, not a big youtuber but doing well) as you can see hasn't negatively affected the channel at all, you have to make the right choices for you, I was disenfrachised with that aspect of youtube and switched to one that more suited me, getting to play games I love once again, doesnt make my channel look weird and has actually got a really cool subbase now, subs more appreciate that you enjoy doing what your doing rather than being a slave to their desires.
Wouldnt say making Lets plays is the key to subs and views either though, I got lucky in that 4 of my Zelda lets plays are now top search results with their shows ( Wind waker/Ocarina of time masterquest/ Twilight Princess/Majoras Mask) as well as a few others, if I hadnt got partnership and the ability to do that with my CoD stuff, they wouldnt be top search results, what I did prior benefited what I do now, I doubt I would be doing as well as I am otherwise.
check social blade first sir before making a thread like this 
