Small business WLAN solution?

Hello all,

I am looking to upgrade the WLAN provision in the company which I work in. Currently we have 4 non-bridged wireless access points. This set up causes many problems in terms of connectivity. The reason we have 4 unique access points, rather than one powerful router is due to the number of client connections rather than the size of the site. Any one of our access points only allows for MAC filtering for 32 devices at any one time. However, when I look at the documentation for more modern equipment no reference is made to a maximum number of devices.
I've been looking at using a wireless distribution system as a replacement to our current WLAN. I have a few questions which I have either not been able to find an answer to or been able to understand.

1) Will I be be able to dictate access via MAC address when using a WDS?
2)Is there a limit to the number of users which can be connected via MAC filtering to any one access point?
3) Is what I'm proposing even the best solution to the issue?
4) Is there such a thing as a router which can filter 50+ clients simultaneously?

Thank you for your help. I appreciate I may not have explained my situation very well. Let me know if I should provide more information