Wardecs were badly designed before, and they’re still badly designed now. Part of the problem is that PvP in general is badly designed in EVE. Thus it is hard to make any wardec mechanic interesting and useful because EVE PvP generally boils down to people who are almost certain they will win attacking people who are fairly certain they will lose. Which leads to avoidance behaviour, not engagement.
To get back on topic however, Capitals in high sec is a really terrible idea. Capitals essentially are a death sentence to everything non-capital. There are very few things in the game that capitals can’t do better than any other ship class. Thus you would remove the growth and development prospects for most other ship classes and all new players by putting them directly up against ships they can’t possibly compete with.
Capitals shouldn’t even be allowed in all of low-sec. Among many other changes that would be needed to bring EVE back to life, High sec and Low sec need changes to make them more interesting. One of those changes would be to limit capitals to something like 0.2 security and lower.
The only usage I can see for ‘capital like power’ in high sec is some structure bashing. Either a Battleship class that is bonused up for larger weapons (like Attack Battlecruisers are for large weapons), or go with the “Pocket Capitals” class of ships between BS and Capital size and allow the smallest/weakest of those in high sec.
Previous discussions on “Pocket Capitals” here (the link itself and the link within it):