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What Enzo said, again. If you simply must have one huge amplifier with different output stages, and it's un-roadworthy enough that you have to design plug-and-play output stages, there are more problems than an easy way to swap output devices.
Solid state amps which fail often have a chain of destruction leading all the way back into the front of the amp. Swapping just the output devices doesn't help, and may in fact kill new, good output stages if the voltage amp, pre-drivers and/or drivers were damaged. With today's parts, the whole front end of the amp before the output stage may be a trivial cost, so, as Enzo notes, why not replicate the whole power amp and mount that whole thing on a heat sink, plugging and unplugging the whole power amp? The connectors are much simpler and more reliable.
In fact, since it's almost certain that you use more than one huge speaker driven by this thing, why not use one smaller power amp per speaker, not many speakers per power amp? That way, a failure of either a speaker or a power amp doesn't shut you down. And bring more speaker/power amp modules than you need, or more power amps (and the associated power supplies, which is another high power/high stress item) as whole modules.
Finally, replacing a TO-3 -OR- a TO-247 or whatever in the field under time pressure and with poor tools, lighting, materials, etc. is a tough thing to do. If you get the fixing bolt tension incorrect, place the insulating wafer incorrectly, use too much or too little heat sink compound, or no heat sink goo, or let a conductive bit fall into the goo, or don't test the drivers, or don't fire it up and test it before frying... er, I mean trying it on an expensive speaker, that's going to make for a very unhappy amp owner.
By now, you've probably gleaned that (a) you asked a bunch of people with firm opinions and (b) many of us think you may be optimizing on the wrong point.
But we're always willing to talk about it.
Solid state amps which fail often have a chain of destruction leading all the way back into the front of the amp. Swapping just the output devices doesn't help, and may in fact kill new, good output stages if the voltage amp, pre-drivers and/or drivers were damaged. With today's parts, the whole front end of the amp before the output stage may be a trivial cost, so, as Enzo notes, why not replicate the whole power amp and mount that whole thing on a heat sink, plugging and unplugging the whole power amp? The connectors are much simpler and more reliable.
In fact, since it's almost certain that you use more than one huge speaker driven by this thing, why not use one smaller power amp per speaker, not many speakers per power amp? That way, a failure of either a speaker or a power amp doesn't shut you down. And bring more speaker/power amp modules than you need, or more power amps (and the associated power supplies, which is another high power/high stress item) as whole modules.
Finally, replacing a TO-3 -OR- a TO-247 or whatever in the field under time pressure and with poor tools, lighting, materials, etc. is a tough thing to do. If you get the fixing bolt tension incorrect, place the insulating wafer incorrectly, use too much or too little heat sink compound, or no heat sink goo, or let a conductive bit fall into the goo, or don't test the drivers, or don't fire it up and test it before frying... er, I mean trying it on an expensive speaker, that's going to make for a very unhappy amp owner.
By now, you've probably gleaned that (a) you asked a bunch of people with firm opinions and (b) many of us think you may be optimizing on the wrong point.
But we're always willing to talk about it.
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