If you are building a building I would build for growth. If you do go with interior collection have a plan to move it outside should the need arise. Hopefully it does, that means you're growing.
You may be better with the collector inside. According to guidelines you are not supposed to hook a wide belt sander to it. Is that a problem?
I am not familiar with your business. Sounds like mostly nested routing and edgebanding?
We just moved and installed an outdoor collector. There are pluses and minuses.
Good:
-Quieter
-Safer
-Easier to empty (we don't empty it, it goes directly into a dumpster)
-Filters self clean
-It takes up zero floor space.
-It can be significantly larger than 5,000 cfm
-Less daily maintenance, much less.
-Fan is after the filter
Bad:
-Its a single system if one machine needs it, it must be on.
-It blows air back into the building that is ~ 15 degrees colder than when it went out in Michigan in winter
-I believe it will increase your electric bill over smaller interior collectors that can be turned on and off based on need.
- Its expensive up front.
As I said earlier make sure you don't do something with the layout of the building and the land that precludes you from moving it outside should it become necessary.
I have an S1000 10hp with dumper, great collector. I am holding on to it in case I have a need far away from our main collector. Probably a dumb idea, I likely will not need it.
I can't help you with the electric vs gas not a choice for me, gas is a must here.
Bill.