I have a really heavy (I mean really heavy) bass guitar. I currently have a strap that locks onto the strap holder, but I'm worried that that could cause problems. When I perform, I like to do lots of tricks with my bass (swing it 360 around my body etc.). I definitely need some kind of lock to prevent the bass from going flying, but should I get a normal strap and just put strap locks on the body or is it fine the way it is?
This is the kind of question where there isn't a one size fits all answer. Not all straps (locking or otherwise) are created the same, nor are all strap locks or standard strap buttons. Some straps have really big, loose holes or slots for buttons while others are tighter. Some strap buttons are bigger than others. And so on.
Personally, I prefer to use strap locks versus a locking strap. This is really just because there aren't a ton of locking straps out there, so choice are limited and it can be hard to find one I like in terms of comfort and looks. By using strap locks, you have nearly unlimited choice in strap designs. This way, you can have a better chance of picking one that's comfy for a heavy bass, and one that you like the looks of.
If it turns out that a strap's slot/hole is way too big and it seems there's a risk that it could slip off a strap lock, I just ignore the hole and make my own by punching through the end of the strap and then enlarging the punched hole with a sharp drill bit, sized to just allow the strap onto the lock.
In terms of locks, I prefer Schaller straplocks, but I have some instruments where I've used other brands to get a matching finish to the other hardware on the bass.
In your situation, with antics involved, I wouldn't bother with anything but a completely fixed strap - screwed in with a large washer under the screw head.
I prefer Dunlop straploks and use them on most of my basses - and guitars. Never had a problem, and feel they're easier to attatch and detatch than others. Generally, the top fitting is permanently attatched - it never needs to come off - so it hardly needs a locking mechanism.
If there's no need to undo your strap from the guitar - it's easy to put it over your head and can stay on in the case - then fit sturdy screws with generous washers instead.