I’ve spent a fair bit of time around that way. I’d agree with comments above Ty-Nant is a bike carry mostly and I’ve walked up Pony but I’ve not biked up.
I reckon if you’re happy to push/carry at times there’s a doable route from Dol up to Cregennen. There’s a path that runs parallel with road, I’ve ridden parts the other way. It starts at a pretty steep grassy bank off a lane then it’s okay dropping you down to YH. You’re back up again then to the lakes.
I’ve never done that route but would be tempted 🙂 down the ramp then to Mawwdach trail.
Lovely part of the world!