Time for Another Spellcasting House Rule

Eventually, I will decide exactly how I want to handle spells in my Swords & Wizardry White Box games. The number of spells that can be cast per day are so scanty at low levels that it's a wonder anyone ever wants to be a spellcaster, especially since magic-users in particular are ineffective at anything other than spellcasting. My last house rule has been unsatisfying (unmemorized spells can be cast, but the casting time is extended to a turn and the caster must make a saving throw or suffer a temporary loss of strength). The casting may or may not have consequences, and even if it does, the cost is negligible. For my next house rule on the subject, I think I'll let unmemorized spells be cast at a cost of 1 hit point per spell level. This is an idea inspired by Microlite20, although in those rules it's the default method for all spellcasting. In Microlite20, the hit point cost is 1 plus double the spell level, but hit points spent in this manner are recovered after eight hours of rest. In my house rule, the hit point cost is lower, but the hit points spent are actual damage and are recovered in the same manner as other wounds (1 hit point per day of rest). This makes it simpler, but it makes the consequences of casting unmemorized spells greater, thus preserving the importance of wisely choosing which spells to memorize. I'll probably also add the Holmes rule for creating spell scrolls. Will any of this work or will I be trying another house rule in the near future? We shall see...