A workhorse, do-it-all stroller for a toddler to nap in, that immediately makes me think of the Baby Jogger City Elite (actually, mostly I think of three-wheeled strollers with swivel wheels frames as workhorse-like). It is long enough (even if there are perhaps longer set surfaces even) - but the space, width, and height to the canopy will allow you to use the City Elite up to 4/5 years of age, for real. Overall, the Baby Jogger strollers with a world-facing-only seat are rather roomy so even with a City Mini GT2 you will do great, I believe.
Next in line, if the BJCE is too expensive or not to your liking, I'd think of the Britax B-Motion 3 Plus (or if a three-wheeler is a no-go, the Britax B-Motion 4+). This is a pushchair that is rather robust-feeling, and the seat length is 1m+. FOr naps of an even older toddler, this will be just fine. The one negative you may find with the Britax B-Motion/B-Agile lines is a rather slanted (not at all upright) seat. Some parents/kids have a problem with that, that is why I say it "out loud."
I'll mention the Valco Snap Trend as well as this is a very spacious buggy with a long seat surface. It is not an all-terrain, workhorse kind of stroller though, as it lacks suspension... but for normal walks, it would suit alright.
Lastly, the Out N About Nipper Single is spacious but with fewer features... and no adjustable leg rest, so the naps are possible but not as comfy as with the other models.
I hope I helped and gave you enough inspiration! 😊 The thing is, the room in the seat is not all - at some point (around 3 years of age), it will still be short to be all straight while napping. The space to the canopy and the width are also important as the child grows and needs, for example, a footmuff in the winter... Good luck and the best of strolls, in any case 😉