Have you heard about the ePMP 3000 AP and ePMP 300-25
This AP will be backward compatible with the force 180 and 200.
ePMP2000 will help out if you're seeing interference but won't inherently improve your capacity. As mentioned, ePMP3000 might be an answer, but looks likely to not be an available option for several more months.
You can overlay PMP450 gear atop ePMP gear, provided you use an available low-interference channel. I don't know about setting PMP450 and ePMP sectors on the same channel and setting correctly so that they don't interefere with each other.
You can also just overlay additional ePMP APs, with the same caveat that you need to avoid interference. (also if two sectors are ~180 degrees apart I expect you'd have a better chance of getting frequency reuse working than with PMP450 overlaid) You can/should also look into using 40MHz channel widths - we don't do that for APs, only for BH links, but the gear appears to work great in that configuration.
Your post isn't clear regarding whether the request to "double ... bandwidth" is per sector, in aggregate, or per SM/camera.
The bandwidth figure is an aggregate number across the system, just adding more SU's with similar upload requirements. I am hoping at least the 3000 SU's are available soon, I see them listed in distribution, but no one seems to have them yet.
I'm going to do some testing soon to see if I can use 40MHz channels, maybe change out my heaviest loaded sector to a ePMP2000 and see how that works.
I'm curious if anyone has done any direct comparisons (or have at least a rough guess) of the improvements in near-LOS conditions between the 450 and 1000/2000 series (I've never used the 450 gear). Debating if the money would be better spent either upgrading to the 450 gear, or establishing one or two more AP locations to improve my chances of LOS to at least one tower.
Just my two cents here...
I would expect based on what you described that 40MHz channels should work and would almost double your throughput. You should only see problems if you cannot find clean channels.
I also like newkirk's suggestion of simply adding more AP's. With the farthest SM at 1.5 miles you should be able to easily deploy in the 5.2 and 5.4 band if the 5.1 and 5.8 bands are congested.
A few things to think about with the AC wave 2 hardware. MU-MIMO is only in the download direction (AP to SM). That will not factor in, or help you with your scenario since you are 90+% upload. Also, if you use 20mhz channels the best modulation you can get with the AC gear is 256 QAM 3/4 (not 256 QAM 5/6) and you need around a -63dbm rssi with pretty much no interference to reach this modulation level. Even if you reach this modulation level consistently , this only gives about a 20% higher data rate than MCS15 with the ePMP 1000/180/200 gear. I can not see upgrading an entire system for a max increase in throughput of 20%.
Personally, I would go the route suggested by Joel and Seth. And if you do add more AP's go with the ePMP2000 Lite. Less expensive than the ePMP1000 synced and better rf filtering.
Thanks for the comments. At this point, I'm planning on upgrading several sectors to the ePMP2000 units, and testing 40MHz channels for viability.
I'm also going to build out another AP location to maximize my chances for a clean LOS to the new locations.