Storage option for capsule hotel

Hi,
Since many hotels around central Japan area (Tokyo, Nagoya, Osaka, etc) seem extremely booked out compared to earlier years I am getting worried of not having any place to stay in case I need to rearrange my plans.

I thought if capsule hotels would be an option but since I carry around a medium sized suitcase and a smaller backpack it could be a bit of trouble. I know the capsules come with a locker but that wont do.

Do you think it would be possible to store it behind the check in desk for a fee? Or are there any reliable big sized lockers or locker rooms that store over night in Tokyo, Osaka or Nagoya?

Any other last choice options that would do in those cities? Bunk beds are fine as long as I can do with my luggage....

Option 1.
Store behind the counter. This is possible. But it depends on whether they have space.
Option 2.
Choose a cheap option but not a capsule hotel like say Hana hostel, or First Cabin. They have storage areas.
Option 3.
Store it at lockers in the station. Though if you are going during a popular time like during a festival, autumn season etc this might be full. Also, if you store the luggage over the stipulated time, it gets taken away by security. The thing is, the security counter may not be open as the securities are patrolling!
Lastly, there may not be lockers (or those large enough) if your hotel's station is not a major one.
Option 4.
Store them at storage areas. These are like cloak rooms for bags. Major station have them.
Option 5.
Post it forward to your next destination. And collect it, swap out what you need and post it again.
Option 6.
Change the way your bags are designed. Multiple smaller bags or even using zip lock bags to save on space.

Finally, an idea.
Have a knapsack or backpack on the ready, while the huge suitcase stays somewhere like a locker. Pack enough in the ready bag and only return to the suitcase to replenish supplies. (sounds like zombie apocalypse)

most hostels i have been has storage/store room to keep bulky bags while small/medium backpacks(sub ~50L) can be brought o bed area.

For capsule hotels, in my experience the configuration may defers from one to another.. for some they have lockers on the same floor of your capsule, some will have lockers on a different floors than the capsule areas.
You should try google for the capsule youre looking into n search for images.
make it the use of locker at train station as last resort, as some of the lockers are opened up daily to be cleared (im not sure how to identify this such lockers, but of course the staff will bring.keep em to claim counter/etc)