How to use JobServer properly to have a certains amount of IRIS processes available amongs multiple Apache nodes ?

I use cspa24.so Apache module to connect to IRIS. I have notified that idle Apache processes will always result in connections being kept open to the IRIS server, and thus some amount of IRIS processes being kept alive (and dedicated to those apache processes) because of those connections.

Eg: if I have 50 idle Apache processes, I will have 50 IRIS processes being kept alive in IRIS even if there is no client connection being made at that time. 

It's even worse with multiple Apache nodes and a load balancer. 4 Apache nodes will result in 4 x 50 = 200 processes being used and reserved for Apache alone (even with client 0 connections). Apache tends to always create more Apache nodes than needed (for possible incoming connections), which results in more IRIS processes being use that needed as well.

I understand this feature might be useful to have a certain amount of IRIS processes available for possible incoming requests but my plan is to use the JobServer instead. The spare processes would be available for any Apache node (or IRIS itself), without the need of CSP gateway to do it by maintaining connections. Is that possible ? (eg: using some settings).

I could set MinSpareServers/MaxSpareServers to something really low, but this mean Apache itself will have very little headroom in case of incoming requests. Additionally, Apache will still reserve/use "too much" IRIS processes after lot of requests as it will take few minutes to cooldown (eg: Apache processes going from 100 to 0). From what I remember, Apache kill one child process per second and per node.

I am aware of the NSD which explicitly kept some amount of connections to IRIS server and thus some amount of IRIS processes alive as well (regardless of the amount of Apache processes). I want to know if there is an alternative.

EDIT:

one of the major downside of NSD (if we ignore the complex setup) is that you have to specify a certain amount of process for each Apache node and it can't be reused between nodes. So if you have 8 apache nodes and allow 256 clients, this gives 8 x 256 = 2048 IRIS processes (which is quite a lot). Reducing the amount is possible (eg: 8x128) but then you have the risk to be to little especially if apache nodes are not perfectly balanced (eg : load balancer might be IP based). It would be good to specify to reserve 1024 IRIS processes globally, available for all nodes.

Would this work : move the NSD outside the apache nodes (which is Linux based) and move it to IRIS server (Windows) ?

So instead of 8 Apache nodes, with 8 NSD processes for each, I would have 8 apache nodes and a 1 NSD process at IRIS server ?
Then I could set NSD to use (and maintain) 1024 IRIS processes, regardless what is set in Apache.
Now the question is what to set in Minimum/Maximum Server Connections ?It's currently set to 255/256