And to recall and utilize the old Tower style with the new development speeds, there's no need to reinvent the wheel — imho, one mine of each resource on the Tower's respawn would be quite sufficient ;) is it even possible to cobble this together quickly — we'd test it right away :)
The main trouble is the low unit speed (hence the need for upgrades), the second trouble is the cost of building and buying (especially considering upgrades), the third trouble is the small range of damage dealers, essentially only Gremlins and Nagas deal any damage, and well, the fourth semi-trouble is the lack of normal heroes.
Say, for Castle to get 6 Cavaliers, you need to spend 6000 on buying un-upgraded ones and enter the stables. For Tower, you need to spend on the Naga upgrade and buying upgraded Nagas 11400 gold, not counting resources and construction tempo.
Therefore, it is proposed to supplement the Tower's assortment with rarely built Genies, Giants, and also reduce the prices for building and buying. And also tweak the heroes a bit regarding starting skills (or strengthen the skills themselves).
Plus, make the prospect of mass-producing Titans realistic — a very serious buff for Tower. For this, Giants need to be placeable in week 1 without hindering development, preferably with Castle. And to make the upgrade prices lighter.