Major Common Property works

After years and years of grief over the installation of new windows we are finally getting close.  The paperwork is through and we are waiting on the SM to share the quotes with the owners (which she has had for over a month).  The price is very likely to be huge so we were wondering if we could create a by law that says that all east facing living rooms and bedrooms will be paid individually by the lot owner at the time of installation.  The cost will be the same for each owner as all lots are identical in size and by doing it this way it is fair and equitable rather than by unit entitlement over a period of many years.  For investors this means they can up the rent when their unit is done and the others don’t have to dig into their pocket until it is time for theirs to be done.  Is this concept legal?  thanks.