Hello,
Okay, I have the following problem:
We want to build a WLAN between 2 houses with WRT54GL an openwrt.
In both houses are one LAN and WAN with a router (not the WRT54GL). Our problem is now that we want to share data and internet between those 2 LANs.

Data is not the problem, but the internet connection is our problem, but we want that we can say “hey I want give only 2Mbit of my WAN speed to the WRT54GL for the other LAN. But the own LAN have full speed and the normal data between this 2 LANs have also full speed.â€
So is there software to manage this in the openwrt? Or has anyone another idea?

We need also the option to switch to a mesh network, but we want to plan more than 2 houses in this WLAN and we think that a mesh is the best solution to connect more people if we need it.

I hope that anyone can understand what I mean.

Basicly you need a lot of iptables.
You need to set up QOS to allow traffic from the other router but only 2Mbit.
You need iptables to forward certain traffic to a certain router. You can't trunk the traffic (I assume because it aren't 2 ethernet ports). And because of trunking is not possible I wouldn't start setting this up. Because there isn't any advantage to this only problems. Because if 1 router is down then some traffic of the other router won't work anymore because it was passed to the other router.