I have attached a small zip at my webpage that makes a few alterations on the standard 1.84 version. You can get it and see if you like it. You will need to open your Medieval - Total War folder and manually place the units text over the existing file. Then open the campmap/startpos folder, and place the other three files over the existing ones there.

The changes are:

1)Peasant revolts set back to their original troop mix,
2)Muslims-only units are 25% larger than normal,
3)Spanish Jinetes are restricted to the Spanish and Aragonese, and have excellent speed,
4)The Mongols start with some Catapults in the late era,
5)The port for Tunisia should now occur in the proper sea, rather than the Coast of Africa.

As you can see, the first two items are the big ones. There is a general consensus that Muslim troops were cheaper but more numerous during the Medieval period compared to Christian units, but in the game this cannot be shown properly due to the 16-unit limit. And since the AI often does not handle reinforcements properly, this handicaps the Muslim factions. Hopefully the increase in size will even things up some.
Price and support costs have been increased by 25% as well.

Note: You will NOT be able to use HUGE unit sizes with this variation. Normal size should be fine, but I don't know about Large size.
The first person who calls in with a crash and turns out to be playing with huge sizes has to hit himself on top of the head- hard. Sisters, if available, could also do the hitting.