You sound like you've been thinking things through thoroughly ! Congrats 🙂
I have a couple thoughts..
~Being allergic to cigarette smoke, you will have to deal with the lingering smells, trash, mess, etc. no matter where they smoke if you let them. No offense to smokers 🙂 but the scent travels and clings to everything. Everything. Smokers who "only smoke outside" will leave butts out there and bring ashes and odor (in their hair, skin and clothing) into the beds they occupy, the kitchen with food and spread it/wipe on the towels. Any fabric (curtains, rugs, linens, pillows) soaks it up. So does wall paint and wallpaper and wood. That's just how it works.
~Pets; pretty much the same story. Hair, odor, muddy paws transfer and stick to all surfaces. Even if it's a super well-behaved critter 🙂 I love animals, really. I just don't want to volunteer to clean up after everyone's pet. Also: dander, drool, spit, sneezing, hairballs, rolling on the rugs/beds/towels/carpet.
We have family members that are highly sensitive to both animal and smoking residues. Therefore, we don't allow these in our home. I'm not sure why another host would urge a new host to take on these sensitive issues. It's Your place, Your rules 🙂 And, you're not alone..there are many people who choose to stay at places that do NOT allow smoking and pets for many of the same reasons outlined. They are thrilled that we don't have lingering odors (either from animal, smoking or from cleansers used to eliminate odors/stains/dirt from animals and smoking).
Make sure you are comfortable with the details involved. Maybe start out conservatively and then branch out to welcome one pet or smoker and see how it goes.
Well, enough said 🙂 Best wishes on your journey !