@Baragon301 - Here's hoping.
Reading through the plot of this movie (which has a few plot holes and conveniences, although that's standard for this kind of film), the part I would change is regarding Gamera healing after Garasharp drains him.
The whole thing with Gamera getting the "solar power healing" ability out of his backside seems to come out of nowhere and feels too convenient - especially when you consider how his heart had to be restarted with electrical cables in vs. Jiger and with lightning in vs. Zigra. Also, it's a somewhat funny irony that he eats coal and oil and has destroyed at least two sources of renewable energy in his past movies yet gains a solar recharge ability here.
As an alternative - and especially since we get to see Barugon's skeleton at the bottom of Lake Biwa - why not have the military and scientists recover the crystals from Barugon's back and, with a bit of technical wizardry, mount them onto maser-type tanks to fire smaller versions of Barugon's "Death Rainbow"?
This could serve both to help Gamera as he gained energy from Barugon's rainbow ray, so it would be more acceptable to help heal him than sunlight, while the tanks could be used against both Marukobukarappa and later Garasharp - even if the monsters ultimately destroy them when the tank's generators are exhausted of their power supply.
If it had been made at the time, it would likely have been the best use of tanks in a monster movie until the Godzilla the Series episode "Freak Show" rolled around (0:50 - 1:45): https://www.youtube.com/watch?v=g3PYs28E2YA