I got it! Fair warning - I'm not responsible for your G450 catching fire.
So you turn on blast conferencing. It's a kind of meet-me VDN.
You can't have a meet-me VDN be the destination.
But you can loopty-loop trunk it through SM.
So let's say you've got VDNs
0000020 - the blast VDN
0000021 - the first bridge of 6
0000022 - the second bridge of 6
0000023 - the third bridge of 6
0000024 - the fourth bridge of 6
0000025 - the fifth bridge of 6
Let's say the AAR code is 8.
Make the blast destinations 80000021, 80000022, etc
In AAR make them pick a sig/trunk on a different domain - like conf.yourcompany.com
In SM, make 000002x from that domain go to CM
Now the blast calls loop thru SM and terminate on the bridges.
But, because you're a wise guy and bridged conference bridges to conference bridges, they both think there's 2 parties on the call and it never drops. Which really isn't a huge deal for you if you design your logic just right.
In the meet-me vector you can have logic like checking if it's idle or full. That's intended to make people wait on hold until a moderator shows up or reject them if the bridge is full, but we can make them be basic logic checks for our little Rube Goldberg machine. The caveat there is that you can only have the vector check the meet-me VDN you're in. You can't check other meet-me VDNs. So we hop along through many VDNs to check.
Let's say it's vector 20 for this for VDN 0000020 and vector 21 for 0000021-25
Vector 21:
step 1 - wait 0 seconds hearing silence
step 2 - route-to meet-me
Vector 20
1- wait 0 secounds hearing silence
2- go to step 10 if meet-me-idle
3- route to 0000021
4- route to 0000022
5- route to 0000023
6- route to 0000024
7- route to 0000025
10 - route to meet-me
Vector processing continues if a route-to fails. So, the first person to dial in brings up the bridge, the next 20 each try the bridges in sequence.
You could have vectors 21,22,23,24,25 instead. I don't think you'd need to go this far though.
vector 21:
wait 0 sec silence
go to step 10 if meet-me-full
route to meet-me
10 - route to 0000022
Either way, it'll only drop if CM does a reset 4, so vector 20 will only ever need to setup the blast conference once to get it up.
You can "stat meet-me 0000020" and busy the ports one by one if you need to bring it down, but you shouldn't have to.