Load-balancing over unequal bandwidth

I work with licensed microwave links which have different bandwidth capabilities depending on model, frequency, spectrum availability, etc. This makes load-balancing across multiple links more difficult, since most protocols want to assume they are all the same speed. The only protocol I know of that takes bandwidth into account is EIGRP, which is proprietary to Cisco equipment. Is there another way to do this besides EIGRP which will work with a wide variety of equipment and vendors?

Here is an example of one of the topologies I am currently working with: diagram In this situation, if I use OSPF or LACP to pass traffic over all 5 of these links, it will assume the traffic should be split evenly among them. This will cause issues once they all approach 250 mbps, since 2 of the possible paths will start dropping packets.

I was able to come up with a solution by assigning a proportional number of VLANs to each link. This diagram shows how they were split up using 50 mbps as a common denominator. I can run OSPF on each of the 36 VLANs, which will share the traffic roughly evenly between them, but more of those VLANs will pass over the links with higher capacity. The issue with this is a limitation on the number of ECMP routes allowed by some equipment. I currently have some Layer 3 switches that only allow 4 ECMP routes between the same endpoints. Others may have higher limits, but if I add an additional planned 600 mbps link between these devices, it will require 48 ECMP routes.

It seems like there should be another solution out there without having to be limited to a single vendor like EIGRP/Cisco. The current Layer 3 switch I am using between these sites is an HP/Aruba 3810M. I have been impressed with the price/performance/features of these switches so far, except for the limit of 4 ECMP routes. A solution which can work with these switches would be ideal. Thank you.