Well, if you have another army based the same then yes no problem. 🙂
Frontage is 20mm sq per infantry fig (regardless of light or heavy/regular – as the rules use a combat bonus which is different value for heavy or lights) and cavalry is 25mm x 50 (so 2 on a 50mm sq base is spot on as multi basing is absolutely fine, many of my armies are multi based)
So for your forces if playing against someone with a ‘legally’ based army (but see above that doesn’t matter between consenting adults) you might need to do as follows –
As Multi basing is fine make an adjustment to troop numbers based on the unit frontages and either add tokens (or standalone figures) to make up the numbers or probably easier simply make a movement tray to the correct frontage size, place figures on top (ideally somewhere near the required amount) and then use a suitable system to record correct starting number of models and deduct as required.
Hope that quick answer assists but feel free to ask more