As a non-pro, I don't think I've used my pneumatic ratchet since I bought my first cordless impact, but after I got my cordless ratchet, I pulled it out of my toolbox and just got it out of the way. Still keep the pneumatic 1/2" impact around, but don't use it much anymore, either.
I always broke out the impact or breaker bar or conventional tool to break loose the tougher fasteners. I know some people want to use a pneumatic ratchet for that purpose, but given the length, I just don't have any desire to regularly put 100 pounds of effort into breaking loose every 50 ft-lb fastener. Given that, I don't see the point in owning a pneumatic ratchet any more.
As for timing cover bolts, specifically, I would think that the tight space may make it hard for either to fit, but the hose would make it even worse, in my opinion. Note, however, that the body size of the 1/4" M12 is the same as the body size for the 3/8" M12. So for a small drive, it is a bit on the big side (I've never messed wiht a 1/4" pneumatic....not even sure I've seen one).