Keep the surviving troops.
Have you ever seen a SUPER easy base, you raid, and you have tons of troops left over?
I always hate this feeling, because I know that I could have dropped less troops with the same result.
When you end/finish a raid, you will have the option to spend a range of 1-15 gems to keep all surviving troops alive.
Only tier 1 troops remaining (1-49): 1 GEM
Only tier 1 troops remaining (50-99): 2 GEM
Only tier 1 troops remaining (100-149): 3 GEM
Only tier 1 troops remaining (150-199): 4 GEM
Only tier 1 troops remaining (200-275) 5 GEM
Tier 2 troops remaining (1-5): 1 GEM
Tier 2 troops remaining (6-10): 3 GEM
Tier 2 troops remaining (11-25): 5 GEM
Tier 2 troops remaining (26-35): 7 GEM
Tier 2 troops remaining (36-45): 9 GEM
Tier 2 troops remaining (46-55): 10 GEM
1 tier 3 troops remaining: 2 GEM
2-5 tier 3 troops remaining: 5 GEM
6 tier 3 troops remaining: 10 GEM
7-10 tier 3 troops remaining: 12 GEM
11-15 tier 3 troops remaining: 13 GEM
19 tier 3 troops remaining: 15 GEM
Depending on the troops remaining, the total gems will add up.
For example: Let's say you have 20 barbs, 2 dragons, and a wizard still alive... That would cost 7 GEMS.
1 gem from the tier 1 section
1 gem from the tier 2 section
and 5 gems from the tier 3 section.
This way, SC doesn't feel as though they are losing money. Since people will be gemming less troops, they will still get more gems.