The bowden is fine - its the big parts fan I was using, and probably mostly the fact that I did a lot of messing about swapping components and fiddling with the hotend which broke it. Nozzle swaps put a fair bit of load on those bosses too and I've done a lot of messing about with those too.
The heatsink cooling fan is really quite a bad compromise on the CR-10 since it also blows on the hotend. That means less stable print temperatures, more energy used to keep the hotend hot, and a limitation of max print temp (also the PTFE limits that). By changing to something like a fang cooler with a ducted fan on to the heatsink you get more even part cooling and keep the heatsink cooling air off the hotend. By also changing the cheap basic PTFE to Capricorn tube you can then print to the CR-10's maximum of 260C easily. It makes a big difference to complicated parts with lots of overheads and also opens up a wide range of materials.
I'm going to redesign the cooling fan I was using, but there are others which don't attach to the hotend heatsink and so won't cause the same problem. My new X carriage will be plenty robust enough either way
Its funny, at the top of the previous page I was saying the CR-10 can't really print anything other than PLA. Mine has subsequently printed PETG, CPE, ABS, ASA, and will be doing nylon as soon as my tufnol sheet gets here
I might even try PC and some of the interesting alloys. The only thing I'm not trying to make it do is flexibles as noted in the Ginnam's thread.
A direct extruder will help with flexibles, and also filaments which have problems with oozing like PETG, but I'm not convinced its worth it on the CR-10. That may be because I'm quite happy to simply build another printer to do things the CR-10 is not good at. The Prusa mk3 for example does have a direct extruder using an E3D V6 hotend, and that's pretty much the reference machine of the cartesian market. But, its known to have clogging problems with things like carbon-filled filaments because they stick to it's all-metal hotend. The CR-10 with it's PTFE hotend will print those filaments absolutely fine. It really depends if you've run in to a specific limitation of the bowden setup tbh. If not, there's little to gain.