You've got it right - that is a trade-off. You're still going to be limited by the external strobe unit recycle time if not using onboard flash, although admittedly those have much bigger caps and batteries and can fire off pretty darn fast when not doing full dumps.
To me the 'ideal' approach would be a mini, TTL-capable, hotshoe-connected unit internal to the housing that just flashes an LED in fast enough sequence to provide preflash, flash, and quench information optically to an external strobe, which provides optical mimicry of that sequence/duration. Since that unit would only be firing off very small LEDs with enough light to illuminate a well positioned fiberoptic sensor, it shouldn't have a slow recycle at all and prevent firing off the camera as fast as your main strobe recycle allows, at least. But no one has marketed something like that yet. (A few of us have built very simple little LED-strobes that just use the 'sync' signal to trigger, but that means no TTL or preflash, just manual triggering.) Wouldn't even have to mount "on" the hotshoe - Ikelite's TTL electronics baseplate probably has room for a couple coin batteries, a few more caps and a FET to fire off a couple small LEDs, and their clear housing would let you mount an external fiberoptic fitting almost anywhere without a penetration.
But right now there seems to be a few TTL circuit options (Ikelite housings cabled to their own strobes, TTL adaptors by 3rd parties), a few optical-TTL options (Inon and others mimicking onboard flash), and a lot of manual options (both electronically and optically triggered). It may not seem like many choices, but we're a pretty small market overall...
- tdpriest likes this