Terfyn is right enough - far easier to use a Camcorder . . . but from yr 1st Post ....
Why do you want to change lenses? It's a right-old game during which time you can get dirt in ( which will only show after you've got home ) and if it's "General photography" then you may miss something while changing from WA to Long-lens.
The only reason Photographers use separate lenses WAS there were no decent Zooms . . . but computer-designed lenses are much better . . . . and camcorder ( Usually) have a smaller sensor so the lens can be lighter with greater range. An HD movie frame is only 2mpx so the need for huge quality is missing. DYOR.
DSLRs have many strengths, but the sheer convenience of a camcorder ( & Size, weight, functionality ), means you need to be very experienced, IMHO, to go for a DSLR and enjoy the inconvenience.
For studio-sets then DSLR is king - if you want to take Ages selecting the Shots trying different apertures, etc. All this while the Actors are getting hungry and annoyed.
For Low-light there may be an argument, but my own CX410 ( with 55x Zoom and super Stab.) was indistinguishable from my NEX5 ( with APSC sensor ) . . . . in late-evening street-scene....where there isn't much colour about . . . . both at "wide" for best aperture. A bit of "noise" is good in a dark scene.
For "Horror" genre: Low-light - it's far easier to fix in Post - and there is less risk to Actors and Crew if they can see the Set . . . If they trip, they may sue . . . . Maybe something to allow for when Budgeting?
Ext. mic input ( & Headphone out), very useful BUT it's not essential as you can ( with difficulty) Sync an external digital recorder. I wouldn't be without mine as a collector of Sounds ( PalmTrack now discontinued), even through my camcorder has Jacks . . . the Audio-only files are FAR smaller, then I Edit, adjust etc. before adding to the V.Editor Timeline.
Terfyn is right that camcorders can make good stills - and with the long zoom you can have more pixels that a good DSLR that's been cropped. My own CX410 is 55x (~ 700mm eq.) and 9Mpx - so I can better an APSC DSLR with 135mm limit - also the stab means it works hand-held ( in daylight tbh ).
Good Luck