The major issue with national troops is the lack of decent shield infantry, you'll have the highest turnover of these so being able to replace them easily is important.
You can replace the European Mercs with a mixture of Scottish Swordsmen and German Pikemen, Swordsmen in general are better than the Euro Mercs as they have good reach and no close range issues but are inferior vs cavalry, the pikemen are the opposite, so they balance each other out.
If you can find decent national troops with heavy armour and shields, let me know!
**EDIT** Reiters (of all nationallities), Hussars, Armoured Cossacks and Noble Guards are all good as well, although I use them only in sieges (they are mounted in open field combat making them unsuitable).
As a side note, using the tactics above I managed to defeat 900-ish of 1134 with 119 men (9 heroes + myself) A little over half of mine were wounded/dead by the time they gave up.